Epic Cards Battle

https://imgur.com/a/C9g1Bc3

Note: The two Overlords on JesterBlaze side were previously Jokers if that matters.

At the time of this screenshot one of my Overlords was attacking a Mutant (who had 30% HP Drain Rate) and the Overlord next to him took 1343 dmg and was destroyed. I'm thinking this is a bug though I don't know how the Mutant's HP Drain Rate ability works.

Please attach the image and paste it in post.
Did the Overlord activate it's ability?

Yes, the Overlord was under 800HP and had drawn HP from Treant as I recall.

Then that's its ability?