While held, non-ghost enemies leave behind small, red ghosts on death; using the item causes the ghosts to explode, dealing damage to nearby enemies.
The damage exploding ghosts deal is equal to 3 + 0.04x the health of the enemy the ghost spawned from, and each explosion can hit the same enemy up to 3 times. Explosion range increases the more powerful the explosion is.
Enemies with high health, such as champion enemies, minibosses and bosses will leave behind a larger ghost that creates three explosions, instead of just one.
Explosions from this item do not damage the player or terrain, but can destroy enemy projectiles.
Can be used as long there are ghosts in the room.
Ghosts can be moved by shooting at them.
Ghosts that are currently not visible on the screen (e.g. in larger rooms) will not be detonated when using the item.
Book of Virtues: No wisps are created when using Vade Retro. Instead, ghosts created by enemies very slowly move and shoot tears in the same direction Isaac is shooting. The ghosts' tears deal 3.5 damage, and are fired once every second.
The item's name refers to the Latin phrase "Vade Retro Satana", a phrase commonly uttered during exorcisms which roughly translates to "Stay back, Satan."
This item's ability could be a reference to Nuclear Throne, where the character Melting has a similar ability.
This is further reinforced by the fact that more powerful enemies leave larger ghosts that explode into 3 small blasts; in Nuclear Throne, larger enemies' corpses would explode in a similar fashion.
This item can be used one more time during Isaac's death animation, which will generate a white explosion on his body.
This is another parallel to Nuclear Throne's Melting and his ability, he was also able to use his ability one last time after death to explode his own corpse.
The presence of the (currently unused) Exorcist enemy creates red ghosts that are identical to those created by Vade Retro. These ghosts can even be blown up if Isaac has the item.