Didn’t get a chance to take a screenshot but I think what happened is this:
Playing full beasts as Rafaam, I bought a new hero power and got Lich King. Fast forward a few turns and I have 3 gold left with a new hero power spell on the board. I use Lich King on one of my t4 beasts (the ones that buff +1/+2) and then buy the new hero power, geting Terron Gorefiend’s. At this point I use THAT hero power on my reborn Metalhead, since doing it on one of my other beasts would grief me since they all summoned bugs and the reborn wouldn’t trigger
When combat started, the tier 4 beast that I had originally use the Lich King hero power on (and it still had reborn when combat started) instead played the Gorefiend animation (and was later resummoned appropriately) but NOT the Metalhead I had actually used the HP on.
Pretty weird, but probably has something to do with aura effects and when they wind up on the stack? Says the nosy software engineer.