Dungeon Crawl Classics has some interesting choices for dealing with this week’s scenario. I would still have the falling rocks do 1d6 damage to the player characters. (I might roll a funky die to determine how many rocks fell. A d7 feels right, scattered across the characters of course) Instead of a Dexterity save, I would use a Luck check. The reason I choose to use Luck over Dexterity is that the ability to hang onto a rope or steep wall face with rocks falling down on you seems more of a matter of luck than dexterity to me. Plus I think Luck is just more fun mechanic. If you wanted to use a more conventional Dexterity Save, I’d used DC 15.
Init: +0; Atk spear +4 melee (1d8+1), crossbow +0 (1d6 range 80/160/240 ); AC 16; HD 3d8; MV 25’; Act 1d20; SV Fort +6, Ref +0, Will, +0; AL C
Winged Warrior Sentinels can once per encounter take a full round action to transform into a stone statue for 5 rounds. During this phase, their armor class becomes 20 and their hit points are restored by (2d8).
These guys are supposed to be tough to kill but are slow and have weak saves so they should be vulnerable to spells.