Fresh bug with this card.
I had 2 Glacieon in the game, EX on active, GX on bench.
Both had high damage counters (around 15 I think)
Opponent used magical swap to take the damage from the EX back and forth between the GX and itself (i'm guessing to troll)
He ended up moving all the damage to the GX which knocked it out.
While the card was knocked out he was able to move the damage counters from the GX back over to the EX knocking that out too, now leaving the GX with survivable amount of damage HP, but it was already knocked it.
With no cards in play my turn still started, after drawing a card the GX randomly glitched back in from the discard pile with HP not equal to both how we started and how it finished.