"Self Subterfuge" Damage

In my last game playing as Brand, my team engaged in a teamfight in the jungle near Baron. I was standing near the outside of the fight and didn't seem to be hit by anything major but I quickly was bursted down. On the death screen, it said I took 1250 damage from "Self Subterfuge" (1050 from one source and 200 from another) and there were no tooltips for this whole self subterfuge category. We went on to lose the fight and quickly the game. I was wondering if this self subterfuge damage was a bug or what champion would have done the damage. I was facing Annie, Lucian, Lux, Swain, and Shaco while Blitzcrank, Garen, Sivir, Brand (me), and Nunu (disconnected).

Any idea where this damage would have come from?