Yeah I have experienced this, my heroes also does this every now and then, there's 2 masteries both at tier 5 in the defense tree of materies (green) that allow those heroes to do this

1. Retribution: 50% chance to counter attack when the heroes in question lose 25% of it's max HP from a single opponent skill

2. Deterence: 20% chance to counter attack when enemy applied freeze, stun or sleep to allies.

JoinME said:

Fast hegemon? 

Not Hegemon - I've seen it from random champions - but mainly from Rotos , Trunda, Tormin, Foli  or Madam Serris.

OzzLee said:

Yeah I have experienced this, my heroes also does this every now and then, there's 2 masteries both at tier 5 in the defense tree of materies (green) that allow those heroes to do this

1. Retribution: 50% chance to counter attack when the heroes in question lose 25% of it's max HP from a single opponent skill

2. Deterence: 20% chance to counter attack when enemy applied freeze, stun or sleep to allies.

edit: whoops I didn't read it correctly at the first time, yeah Joinme might be correct and I am most likely wrong

Yeah, I haven't attacked yet so can't be retribution.  Possibily Deterence though.....

What team do you run?

I'm almost positive it's Deterence. Happens to me a lot with Tormin. 

Lxzy said:

What team do you run?

I'm almost positive it's Deterence. Happens to me a lot with Tormin. 

I definitely see it alot when I run Tormin - I'll pay attention to see if it's happening with other team comp's as well.