Can someone please explain the lead image to me before I send it off to the lab?

I just used this trick to beat someone with their own Nozdormu in a real game. We were playing this week’s Tavern Brawl that fills everyone’s deck with Unstable Portals, a card that plays a long animation and summons a random minion. He used it to drop Nozdormu on me, which is a terrifying enough card own its own as…