Assassin's gift...

[Methona]

When I equip my xbow I get a lot of spam from the fillies, but also this message:

(Combat): You are affected by your assassin's gift.
(Combat): Your melee and ranged attacks inflict an extra 4d6 + 1d6 per epic level of acid damage.

Where did I get this gift ?
Was it an xmas present, or somewhere else ?
Wiki knows nothing, or atleast is not telling...

 

[Terranigma]

It is part of the old Long Shadow filigree set bonus when you had 3 or more Long Shadow filigree. The old effect used to be dealing an extra 4d6 + 1d6 acid damage per epic level. This was modified (as were other filigree sets) to instead grant extra Imbue dice instead of distinct forms of bonus damage. The description debug text was never modified or removed when the Imbue change happened.