Feedback about monster
I couldn't find a Giant Worm creature that's not a Lindworm, so I wanted to make a giant earthworm-like creature with sharp teeth, tunneling capabilities, and various acrobatics that wouldn't overwhelm a lone PC with the double initiative draw ability. I'm not very good at making these things, and my writing has suffered due to time and the late hour, so I would appreciate feedback!
Giant Mountain Worm
The giant creatures prowl the subterranean areas of mountains, tunneling to create vast underground networks connected to clusters of natural caverns.
Ferocity: 1
Size: Large
Movement: 14
Armor: -
HP: 20
Monster Attacks
D6
1 Ferocious Bite!
2d8 slashing
2 Watch your footing
Worm tunnels under to the nearest opponent, doing d6 Bludgeoning and doing d6 damage while PC is inside until either the worm is dead or on a successful Acrobatics roll.
3 Pummeling Smash
Worm whirls straight ahead at the nearest opponent, doing 2d6 Damage and target is knocked Prone
4 Flanking Attack
Worm tunnels under to an opponent in the rear, emerging and doing 1d8 slashing with its bite.
5 Strangling Twist
Worm wraps around the nearest opponent, immobilizing them and doing 2d6 Bludgeoning until a successful Brawling roll by the opponent
6 Ceiling Collapse
Worm leaps straight towards the ceiling, breaking and dislodging rock on top a random opponent. 2d6 Bludgeoning, opponent is knocked Prone and must make a successful Acrobatics to escape.