I was wondering how to rule something in my friend's campaign.
We were fighting a modified beholder boss as a level 13 druid and a level 12 warlock. The fight was at a large summoning circle at the bottom of a 250-foot hole with a diameter of 15 feet. I, the druid, was at the top of the hole and the warlock was levitating up the hole after getting the beholder's attention.
I proceeded to use the move earth cantrip to drop 5 feet of stone on top of the beholder as it was rising up. How much damage should this do?
After a couple rounds, the beholder started to go back down after taking a lot of damage. I noticed this and polymorphed into a T-Rex and jumped in the hole. How much damage should the beholder take on impact if the T-Rex hits it, and slams it into the ground?
We then proceeded to fight the beholder which summoned 3 devils and eventually won.
TLDR: I fought a beholder in a 250-foot shaft and jumped in as a T-Rex and smashed it into the ground. How do you rule that for damage to the beholder?