Sacrificial Dagger

Sacrificial Dagger is an unlockable passive item.

Effect[]

Gives Isaac a sideways dagger that orbits him, dealing high damage to enemies on contact and blocking enemy shots.
- The knife deals 15 damage every 1/15th of a second (every 4 frames) or 225 damage per second.
- The knife deals 15 damage every 2/15ths of a second (every 8 frames) or 112.5 damage per second.

Sacrificial Dagger deals the highest amount of contact damage out of all orbitals.
The dagger orbits further away from Isaac than many other orbital familiars (minus Big Fan), making it easier to use both offensively and defensively.

In the original Binding of Isaac, Sacrificial Dagger rotated upright, while in Rebirth it now orbits on its side.
This item is used in Challenge #4 (Darkness Falls).
While the in-game name and Steam achievement name says 'Sacrificial Dagger', when unlocked, the in-game text shows 'Sacrificial Knife'.
The Sacrificial Dagger's description is likely a reference to the Jewish story of Abraham's sacrifice of his son, Isaac (in what is known as, literally, the Binding of Isaac). Abraham took his son Isaac to a mountain to sacrifice his son at the command of God. Despite being commanded to do so, he knew through his faith that God would not allow his son to be sacrificed.