Hieracosphinx

Hawk-headed and lion-bodied, and unlike its cousin it does not ask anything. There is no riddle, no bargain and no conversation. It has a boundary, it patrols the boundary, and things that cross the boundary are removed. It has done this for four hundred years with the unhurried competence of a creature that has never once been argued out of a decision.

Stoop: piercing, melee 10 ft, +5 to hit, 2d8+3, made from above at the start of any encounter it begins in the air. Raking Claws: slashing, melee 5 ft, +5 to hit, 2d6+3, its second attack each round. Screech: 30 ft, save Wis Mind, fail save roll 2d6+2 psychic, cooldown 3 rounds, used to break a line rather than to kill.

The Boundary: it fights only within its patrol and does not pursue one step beyond it. Withdrawing over the line ends the encounter immediately, whatever its remaining HP and whatever has been done to it. No Riddles: it cannot be delayed by conversation, negotiation, riddling or appeals of any kind, and creatures expecting otherwise lose their first round finding out.