The projectile deals damage equal to Isaac's damage +2, and has a cooldown equal to 2x Isaac's normal tear rate.
Holding an attack button charges a spin attack, ready when the sword flashes, which damages all enemies around Isaac. It also deflects enemy projectiles, which can damage enemies who get hit, and launches a projectile regardless of Isaac's current health.
The circular swing deals 8x Isaac's damage +10, and the projectile created from it deals 4x Isaac's damage +4.
The charge time is based on Isaac's tears stat, at ~4x Isaac's normal tear rate.
While charging, the sword will damage the first enemy that contacts it. This will cancel the spin attack.
Spirit Sword has the highest priority of all tear modifiers in the game, over Epic Fetus and Mom's Knife.
Unlike most charge attacks, the direction of the attack can't be changed by pressing and holding a different attack button then releasing the old one. Instead, it will stay pointing the same direction until all attack buttons are released, either doing nothing or using the spin attack, or the sword touches and damages an enemy, dealing sword slash damage.
Spirit Sword can be used to open Spiked Chests and Mimics without taking damage.
Range upgrades move the hitbox of the sword forwards, including the spin attack. Enough range upgrades can leave a large blind spot directly in front of the sword.
Only the projectile and spin attack are affected by tear rate, not the normal sword swing, meaning that items that increase damage but decrease tear rate, such as Polyphemus and Eve's Mascara, are much more effective when only using the swing. Additionally, items that do the inverse, such as Soy Milk and Almond Milk; are not as effective when only using the swing.
Spirit Sword will deflect Mother's Fistula attack and will send it right back at her, entering a short sequence that allows to deal bonus damage, if executed correctly; see the page for more details.
Fire Mind: Sword strikes and beams can burn enemies, and beams have a chance to explode.
The Forgotten: Spirit Sword will only work with The Soul, no changes to The Forgotten.
Godhead: The fired projectile receives Godhead effects. No effect on the swing aside from stat changes.
Incubus: Incubus tears are replaced with a sword, identical to Isaac.
Ipecac: Sword beams are exploding shots that deal Isaac's damage — does not apply Ipecac's +40 damage modifier.
Caution should be taken as having full red heart containers (or no red heart containers) will cause a sword beam to always fire when using the regular swing which means any swing (or any spin regardless of red heart containers) will damage Isaac when using the sword at melee range unless he has explosion immunity.
Jacob's Ladder: Both the sword shots and sword swing create electricity.
Jacob and Esau: Knockback from the sword will separate the brother carrying the sword from the other.
When combined with Technology, the sword becomes a lightsaber, which is a reference to Star Wars.
The name Spirit Sword is a reference to the Sword of the Spirit, one of the many armaments that make up the Armor of God. This is further supported by the fact that it is an Angel Room item.
PC MMXC VV2C (Starting item as Eden)
When reaching 30.00 Tear Rate or higher, Spirit Sword will continuously use the spin attack, only stopped by holding down a fire key. This is likely due to the fact that starting at 30.00 Tear Rate, the internal number is "0", and begins to go negative beyond that.
In waterlogged rooms, the reflection of the sword swings in the opposite direction of the actual sword, when it should swing in the same direction.
Having Hemoptysis with Spirit Sword will sometimes cause the game to crash when hitting both at once.