Exotic Almond

I had a group playing DnD at my house on Friday and the final bosses of the dungeon (not campaign) were summoning a Dragon-blood Ooze (an ooze made from dragon blood) in a summoning circle. The paladin LICKED the circle and then before I could say anything rolled a 20 on a die (I wasn't going to call for a save) with that luck I had to do something so I turned them into an adult amethyst dragon as if they were affected by a potion of dragon's majesty (turn into dragon for 1 hour). He 1 shot every enemy and the whole party although luckily the party wasn't killed outright and everyone succeeded in the death saving throws. I now regret this as it ruined my boss fight. (Although it was pretty funny)