whats with bite down?

[1818 English Bicycle]

whats the purpose of this i picked it up in the abandoned dungeon awhile back said it would just kill me so i havent used it.but is there a purpose for this? or is it just there for realism or just ♥♥♥♥♥ and giggles. just curious is all

[Celltastic]

when you normally die and ressurect, your second ressurect is blocked until you get a deathblow, with the bite down that restriction does not exist and you can ressurect a second time without getting a death blow, alot of pepole use the bite down when they are on low hp, they kill themselves with bite down and get back to half hp, and they still have their seond or third ressurect still available to use without getting a deathblow