Win Condition Druid Card PLEASE HELP

I took a break from hearthstone and have since returned.

I played a druid deck today with almost no minions, he spent the entire turns gaining mana crystals and drawing cards. I had 30 health and 10 armor and on his last turn he played a card, without attacking I was defeated. Dazed & perplexed by what just happened I didn’t get a chance to look at what card just defeated me. Can anyone shed some light on which card that might have been? I didn’t think there were any win condition cards available.

There is one , forgot the name , that if it is the last card you play the enemy dies . Meaning you have to have 0 cards in your hand , deck and battlefield then play it . Stupid really , especially for druids that can draw 20 cards in one turn .

Assuming this is wild, and Mecha’thun druid. I played it for a couple years as my main wild deck. It’s actually a decent deck if you play it right, and dew process really helped it. Warlock was the go-to Mecha’thun for the most part, with a rogue version floating around.

Found it, Mecha’Thun, stupid dumb