Can someone help me?

i have a festering essence of destruction but i dont know what it does (it looks like a pile of neon powder) can someone tell me what it does and how i can use it?|||Since they added the 1.13 patch, those essences can drop from act bosses.
Twisted Essence of Suffering(Andy/Duriel)
Charged Essense of Hatred(Meph)
Burning Essence of Terror(Diablo)
Festering Essence of Destruction(Baal)
Stick one of each in the cube and they'll make:
Token of Absolution - Grants another Respec opportunity aside from the 3 Akara can grant.
They also have some trade value, although I wonder why since they're fairly easy to obtain.|||I wonder can those essences drop in "single player"?