If Isaac walks into a library for the first time with NO!, The Book of Virtues is very likely to spawn.
Because of this, when acquired from a library the book cannot be rerolled by use of the D4, D100, a Dice Room, or getting hit as Tainted Eden.
Whenever Isaac is invulnerable the wisps are as well, but can still deal damage.
If a wisp is damaged, it will be smaller in size.
Summoning a wisp while at the maximum will replace the most damaged wisp.
While having 100% chance of Angel Room discovery, Isaac will not get teleported to a Devil Room by using some items which allow it. Instead, he will be teleported to the Angel Room, keeping his 100% chance of discovering Angel Room. This can be used to get to Angel Room on the first floor, where naturally Devil/Angel Rooms do not spawn, and still keep the 100% chance for the next floor.
Gluttony: a heart wisp similar to Yum Heart's wisp (middle ring, takes 3 hits, may drop heart on death).
Sloth: a Bob's Head wisp in the middle ring. Their tears travel in an arc like Ipecac but don't explode on impact. There is a small chance for an exploding tear.
The Boomerang: Any wisps created with The Boomerang will disappear when changing rooms. Tears fired up by those Wisps will fly back to Isaac after traveling the same range as Isaac's.
Box of Friends: The wisps are Black with a dark aura, and shoot dark tears.
Box of Spiders: Spawns 5-6 spider-like wisps (maxed at 12) hovering on a distant orbit. They fire small spectral tears, deals contact damage, and transform into blue spiders upon destruction.
Breath of Life: Creates a wisp after it's been held long enough for Isaac to take damage.
Broken Shovel: The wisps become tiny ghosts reminiscent of The Soul. When a tear shot by the wisp hits an enemy, there's a chance for Mom's leg to stomp on them.
Brown Nugget: The wisps are brownish and do not fire with Isaac, but instead auto-fire at nearby enemies like the Nugget's fly turret. The wisps are lost after leaving the room they were created in.
Butter Bean: Inner ring. The wisps are white and do not shoot tears or deal contact damage, only 1 health each, release farts that knockback upon death and cannot be carried across rooms.
The Candle: Wisp are blue and only exist within the current room. For each activation of the candle, a new wisp is added for the duration of the blue flame. If the wisp stays after the flame disappears depends on the type of charge used to activate the blue flame: For a green charge, it only stays if the generated blue flame hit an enemy. For a blue charge, the wisp always stays. Wisps are reset to one if the blue flame does not hit an enemy.
Clear Rune: Spawns a purple-glowing rune wisp. Wisps fire normal tears and drop runes and soul stones when destroyed. They also have a 15% chance to drop a random rune when they kill an enemy. Even though they're colored purple, they do not have homing properties.
Dataminer: Randomly consuming enemies and transforms them into wisps with random effect. Activating Dataminer creates basic blue wisp.
Dead Sea Scrolls: Each wisp spawned has attributes of the active item that was triggered.
Decap Attack: Spawns stationary a wisp at the location of Isaac from that fires in the direction of Isaac's tears. No limit of wisps persisting. Wisps only last for the current room.
Deck of Cards: The wisps have a card-like appearance, reside within the inner ring, and spawn a card when destroyed.
Delirious: Generates a white wisp that resembles one random boss in this list: Loki, Monstro, Duke of Flies or The Haunt. Loki wisp will fire tears in 4 cardinal directions or diagonal directions, alternating between both; Monstro wisps will fire a cluster of tears like the real Monstro does; Duke of Flies wisps will create blue flies; and The Haunt wisps will fire Brimstone beams that deal 1 damage per tick.
Diplopia: All existing wisps are doubled, and a special Diplopia wisp spawns. It is very durable and has double shots.
Doctor's Remote: Generates a wisp with a bomb-like appearance and grey aura. Wisps fire small grey tears when Isaac fires tears. When Doctor's Remote is activated, normal tears will fire from the wisps, followed by two separate rounds of larger, lighter grey tears, which explode on contact. Explosions will hurt Isaac. Tears fired from wisps surround the targeted area if close; if Isaac has more than four wisps, the tears will form a circle around the missile.
Dull Razor: Inner ring. Adds a grey wisp that has extra durability and does not fire. Touching a Curse Room door or spikes will not deal damage, instead destroying the wisp.
Eden's Soul: Spawns a random wisp. Until the end of the run, if destroyed, a new one will spawn whenever a room is cleared.
Eraser: Spawns a pink eraser wisp. Fires tears and erases enemies on contact. Will not be damaged by blocking projectiles.
Eternal D6: Has a 50/50 chance to either spawn an eternal white-glowing wisp that cannot be destroyed or remove all previously spawned eternal wisps. Wisps spawned from other items cannot be removed.
Flip / Tainted Lazarus: Spawns a small white Isaac head wisp after a flip to the form of Tainted Lazarus that is not holding Book of Virtues, even if Flip was not activated manually.
Flush!: Generates brown wisps. Creates 1 wisp, plus 1 additional wisp for each enemy transformed into poop.
Forget Me Now: Spawns a white wisp with Isaac's head. Wisp cannot be destroyed but disappears upon going to the next floor.
Fortune Cookie: Spawns a green, middle-ring wisp which effects the players luck. These wisps act as a luck upgrade, all but the first will give 0.2 luck. The luck will not go away immediately if the wisps are destroyed, rather it is re-evaluated when a new wisp spawns, so the player may lose all their wisps but maintain their luck until they spawn a new one. Wisps generated by other items will not re-evaluate the luck, so it is possible to discard Fortune Cookie for another active item and keep the luck upgrade permanently, even once all of the green wisps are gone.
Free Lemonade: Spawns large, yellow wisps that will spawn small puddles of yellow creep every two shots. The wisps have little health.
Glass Cannon: The wisps are white, firing larger shots that normally does 8 damage. They are very easily destroyed and are all lost at the same time. If Isaac has wisps from other active items, they are not destroyed when Glass Cannon wisps are.
Guppy's Head: Outer ring. Spawns 2-4 fly wisps which shoot normal wisp tears in place of the blue flies it normally spawns. Upon being destroyed wisps spawn a blue fly.
Guppy's Paw: Converts one red heart container into three wisps. The wisps have small hearts inside and a large amount of Health.
Head of Krampus: Spawns red wisps that fire red tears. Wisps cause a Head of Krampus effect when destroyed.
The Hourglass: Spawns hourglass-shaped wisps that cause a room-wide slowing effect when destroyed.
How to Jump: Spawns stationary a wisp at the location jumped from that fires in the direction of Isaac's tears. Max of 6 wisps spawned this way. Wisps only last for the current room.
Isaac's Tears: Instead of firing tears in a radial pattern, 6 wisps are spawned at the same time. They are destroyed in about 3 seconds, and no more than 6 can be created this way at the same time.
IV Bag: The wisps take the appearance of a coin within the outer ring and fire blood tears.
The Jar: Consumes stored hearts to spawn heart wisps, rather than releasing heart pickups. Heart Wisps has a chance to drop a half red heart when destroyed.
Jar of Flies: Wisps will contain the summoned flies, releasing them when destroyed. Each Wisp can contain up to five Blue Flies, for a possible maximum of four Wisps. Enemies killed by wisps will not add any flies to the jar.
Jar of Wisps: The wisp amount spawned is doubled with one more added.
Kamikaze!: The wisps appear as sticks of dynamite, firing explosive shots. Although the explosions are small and weak, they can still harm Isaac if too close. The wisps also explode when destroyed.
Keeper's Box: The wisps appear as a coin, glowing in yellow. Wisps fire normal tears.
Kidney Bean: The wisps are purple and leave behind a charm cloud when destroyed.
Larynx: The wisps turn red, firing high-damage tears. Tear damage depends on the charge used when the wisps are spawned; At max charge it does 18 damage per tear.
Lemegeton: Gives the purple wisps purple homing tears, also buffs the health of the Lemegeton spirits.
Lemon Mishap: The wisps are yellow, leave behind a yellow creep and shoot faster.
Magic Fingers: The wisps become coins, but fire normal tears. The wisps have a chance to drop coins when they die.
Magic Skin: The wisps are pink, but fire tears that have a chance to poison enemies.
Mama Mega!: Spawns 8 golden bomb wisps. When destroyed, the wisp spawns a golden troll bomb which can damage Isaac.
Meat Cleaver: Spawns 1 orbiting red wisp upon use, also cleaves each current wisp, doubling them while reducing their damage. After a wisp is split 3 times, repeated uses will extinguish it.
Mega Bean: Spawns a tiny magenta wisp with high tear height. Upon being destroyed, poisons or freezes enemies in the room.
Mega Blast: Spawns red wisps that utilize a miniature Brimstone as their weapon, which requires charging and releasing as usual. When Isaac uses Mega Blast, each Mega Blast wisp will continuously fire their Brimstone beam outward as they orbit Isaac.
Metronome: Spawns a wisp based on the item that Metronome chooses. For example, if Metronome chooses Spirit Sword, the spawned wisp is a sword that fires sword projectiles. [More info needed]
Mine Crafter: Spawns one glowing green wisp that floats around the room and bounces off walls. Disappears once the room is left. The wisp explodes if hit by Isaac's attacks.
Mom's Bottle of Pills: The wisps are pills in the inner ring. The wisps come in random colors (Blue, Red, White, Pink, Gray, Light Blue, and Yellow). Each color may fire tears that confuse, poison, petrify, burn, or spawn troll bombs. Like pills, these effects are assigned to a random color each run. May drop a pill when destroyed.
Mom's Bra: The wisps glow red, and fire normal tears with a chance to fire a red, petrifying tear.
Mom's Bracelet: Spawns three rock wisps that orbit around where the rock was thrown. The wisps stay in place and shoot to the same direction as Isaac, and they despawn after you leave the room.
Mom's Pad: Wisps are black with yellow fire, with chance to fear.
Mom's Shovel: Spawns 2 wisps. One wisp looks like the Forgotten's body that has more health. The other looks like the Forgotten's soul that fires normal tear.
Monster Manual: Spawns a random wisp within the inner ring with a random tear effect. Multiple tear effects can sometimes stack on a single wisp.
Monstro's Tooth: The wisps are teeth, which shoot teeth at a slower fire rate and deal 12 damage per teeth.
Mr. Boom: The wisps look like small bombs and become mini homing bombs when destroyed.
Mr. ME!: Spawns a wisp that looks like a face in the middle ring and is incapable of shooting tears. The wisp will seek out and open any blocked/locked door, including challenge rooms, item rooms, alt path doors, secret rooms, etc. The wisp can also seek out locked chests and open them. Wisps will extinguish once they have completed their task.
Moving Box: Spawns a box wisp in the middle ring. Only spawns a wisp when dropping items from the box.
My Little Unicorn: Spawns one rainbow-colored wisp while active. These wisps can take more damage than normal wisps, and deal 15 contact damage per tick. When de-activated, the rainbow coloring slightly fades away.
Mystery Gift: Spawns one random wisp. After used, any destroyed wisps on the same layer have a chance to be replaced with a random wisp after a room is cleared (wisps on other orbits are unaffected).
Notched Axe: Has a chance to spawn a black (2.5 damage, A Lump of Coal tears), silver (4 damage, Iron Bar tears), gold (3.5 damage, tears turn enemies into gold), red (3.5 damage, laser tears) or cyan (7 damage, quadruple tears) wisp upon breaking a rock. Also spawns a larger wisp with a larger radius when a poop is mined.
The Necronomicon: Spawns one black-colored wisp within the inner ring. If the wisp dies, it activates the Necronomicon effect in the room.
Pause: Spawns green wisps that temporarily freeze enemies when destroyed.
The Pinking Shears: Spawns a wisp in the form of Isaac's floating head that fires piercing spectral tears.
Placebo: Spawns a white wisp that will drop a random pill when extinguished.
Plan C: Spawns 8 red wisps that shoot red tears with 12 damage per tear. Using Plan C will kill Isaac as expected, but wisps won't disappear if used with an item that grants an extra life.
Plum Flute: Spawns a wisp that uses Baby Plum's diagonal attack whenever the Baby Plum spawned by the flute does the same.
The Poop: The wisps resemble miniature Dips and hover far from Isaac in the outer ring, firing small brown tears that deal 1.5 damage per tear but have a small chance to turn enemies into poop.
Portable Slot: A different wisp is gained depending on what is won from the slot machine. Because of the varied wisp type, 20 wisps can be generated: an inner ring of 8 and an outer ring of 12. Heart wisps can take an additional hit before extinguishing. Key wisps can take the place of normal keys when colliding with objects. Instead of flies, you get fly wisps, similar to the interaction with guppy's head. Bomb wisps spawn mini homing bombs when extinguished. If a "Pretty Fly" orbital is spawned, several attack fly wisps are also spawned, which spawn a blue attack fly when extinguished. [More info needed]
Potato Peeler: Spending a red heart creates an indestructible red wisp that actively follow and damage enemies. It still creates the wisp even if Isaac has no red heart containers, which is likely a bug, as it makes Isaac getting attacking indestructible wisps for free. Especially when they're targeting a monster, the game doesn't recognise them as orbital, so Isaac can create unlimited amount of them.
Prayer Card: The wisps are white, heart-shaped, hover within the inner ring, fire Sacred Heart-esque tears, and are harder to lose.
Razor Blade: The wisps are red. Wisps fire bloody tears and have higher health.
Red Candle: The wisps are red. Wisps fire a small flame similar to the one created by Red Candle. Wisps disappear upon leaving the room.
Red Key: Spawns a red key wisp that fires red tears. The wisp has a chance to unlock a red door while entering an unexplored room.
Remote Detonator: Inner ring. The wisps glow red, appear as bombs, spawn from detonated bombs (cluster bombs and troll bombs do not count), and fire tears that may be detonated mid-flight by re-using the active item.
Satanic Bible: The wisps are black, with a red inverted cross. Each wisp grants you a bonus chance for devil/angel room.
Scissors: The wisps are red, firing small arcing bursts of 2-3 bloody tears.
The Scooper: Spawns white-glowing eyeball wisps. Wisps fire normal tears.
Sharp Key: The wisps appear as a key in white flame, but cannot open locked chests. The wisps fire normal tears. If used without keys, up to 8 wisps can be spawned, making Isaac virtually immune to projectiles by repeatedly spamming the space bar.
Sharp Straw: The wisps are red hearts, sometimes healing Isaac when destroyed. Only creates wisps when Sharp Straw generates a heart.
Smelter: Middle ring. The wisps are yellow and have a chance to drop a random trinket when destroyed.
Shoop Da Whoop!: The wisps are white, reside within the outer ring, and act otherwise normally, but fire a smaller Shoop Da Whoop laser along with Isaac when the item is activated again.
Spider Butt: Spawns a white spider wisp that fires slowing tears.
Spin to Win: Generates up to eight wisps while charging the item, which are immediately extinguished once the charge runs out. The fire rate of the wisps is based on the speed they're rotating.
Spindown Dice: Spawns one random wisp, then rerolls all Isaac's wisps.
Sprinkler: Wisps spin as they orbit, firing tears in a fashion similar to the sprinkler itself. The firing rate of sprinkler wisps is faster than normal wisps.
Stitches: A brownish, stationary wisp is left behind when teleporting. The wisp fires in the same direction as Isaac. Wisps spawned this way do not persist through rooms.
Sulfur: Spawns red wisps that fire a short Brimstone laser beam similar to Azazel, but significantly smaller.
Sumptorium: Spawns one red wisp for each blood clot absorbed, up to 8 wisps. One wisp is extinguished every time a blood clot is created.
Suplex!: Spawns 3 wisps orbiting where Isaac lands his attack.
Tammy's Head: The pale wisps fire more rapidly, but with a very wide spread.
Tear Detonator: Spawns wisp in middle ring. Wisps have a chance to activate the Tear Detonator effect when being destroyed.
Telekinesis: Outer ring. Tears caught by Telekinesis become wisps. A maximum of 12 wisps can be collected via this method, but the shield made by telekinesis is smaller than the ring of wisps, wisps frequently block shots from being added as additional wisps.
Undefined: Spawns blue-glowing glitched wisps which fire tears with random effects.
Unicorn Stump: Same as the My Little Unicorn wisps, except that they can only be summoned in the middle ring, do not fire tears, and only do 2 contact damage per tick .
Urn of Souls: Middle ring. One wisp spawns for every 2 seconds that the flame is active, up to a maximum of 8 (filling up the middle ring). A wisp will sometimes fire a tiny blue flame instead of a tear. Wisps first spawn upon use of the item, allowing free spawning of wisps by not firing.
Vade Retro: The souls spawned from Vade Retro fire tears in the same direction as Isaac. No orbiting wisps are spawn upon use.