What do you unlock when beating bullet hell ?

[Backbone]

Hey, I just beat bullet hell for the first time and unlocked an item doing so.. it was like a dark grey / black bullet with red spots (lights?) on it, it looked kinda high-tech / sci-fi. Can't find it anywhere on the wiki or in the gungeon's "book" where it lists all items.

Can anyone tell me what that item is ?

[Hoot Hoot]

U unlock the Gungeon Blueprint, which is pretty much map layouts in all floors;
U also get the Riddle of Lead which is the bullet u mentioned, which is a buff to several things , namely an heart container, more damage, faster rolls.

[wafflekitty]

Gungeon Blueprint, which will reveal all floors for the remainder of the run. Including secret rooms.

Riddle of Lead, which provides +1 HP heart, +25% damage, +10% speed, and +15% faster dodge rolls, fully heals the player when initially picked up, and gives a 50% chance to negate a damaging hit when at 1 heart or less of HP.

Both items are S-quality.