In my campaign (I haven't started it yet) I'm working on a homebrew first section progression (I know that over planning is not good as a dm) from what I've been told. But I want my players to begin the campaign in a colosseum and during the fight with an owlbear a Bulette bursts through the ground and tackels the owlbear most def killing it and landing behind the players and in front of them is a large hole. I want the players to flee into the hole (bit worried they will try to fight it)
if they decided to head into the hole it would lead to a cave that leads into a abandoned mineshaft littered with the skeletal remains of Kuo-Toa. (this has ties to a lore stuff I have worked on)
What do you recommend for encounter ideas down in the cave or mine? I've looked at a few sources but found nothing yet that feels right.
The party is starting at lvl 3