Ascomoid

False Appearance. While the ascomoid remains motionless, it is almost indistinguishable from an ordinary stone boulder. A creature that can see it and succeeds on a DC 15 Intelligence (Investigation or Nature) check can discern its presence.

Rollover Attack. A creature whose space the ascomoiod enters must make a DC 14 Dexterity saving throw, taking 13 (2d10 + 2) bludgeoning damage and being knocked prone on a failed save, or half as much damage (but not being knocked prone) on a successful one.

Slow to Move. The ascomoid is slow to achieve full movement speed. When starting from a dead stop, the ascomoid moves 30 feet on its first tun, 60 feet on its second turn, 90 feet on its third turn, and can finally achieve its full movement speed of 120 feet on its fourth continuous turn of movement. Once the ascomoid achieves full speed, it can roll for hours without slowing or tiring. The ascomoid cannot take the Dash action.

Spore Spray (Recharge 6). A 30-foot-long and 1-foot-wide spray of toxic spores extends out from the ascomoid. Each creature in that area that isn't a plant must succeed on a DC 14 Constitution saving throw or be poisoned for 1 minute. While poisoned in this way, a target takes 18 (4d8) poison damage at the start of each of its turns. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.