I was playing arena against a paladin and he played a card that was a six mana 10/10 with rush that when played goes dormant for two turns. I immediately went holy shit that card is insane and after the game I went to look up the card only to find that it doesn't seem to exist. I searched the dormant keyword and rush on the wiki and then looked at every six mana card in the game in the game client and I can't find it. Did I play against a hacker or something or could this be a card from the new expansion that somehow got drafted? I feel like I'm losing my mind.

(I feel like I should add that I am very recently returning to the game with the last expansion that I played regularly in being rise of shadows. Also, this is not clickbait I wish I had proof or the actual name of the card but I just didn't think about it until after the game because I thought I could find it online.)