wtf is Death's Sigil

[D3N]

So last time i played was on April, yesterday i opened the game again, and i was like, omg this all this new stuff, the city, new hud omgomgomg the game looks amazing now, BUT THEN when i was farming bosses i dropped "Deathìs Sigil" and i dont find on google what is that thing, can you tell me pls ? :D

[Nito]

Look here[herosiege.wikia.com] buddy.