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From Pathfinder Dark Archive (Remastered), which isn't enabled.

Shrouded Assailant

COMPLEX HAZARD 17
Stealth +33
Description A spirit steps out of a covered mirror, pulling off and becoming shrouded in the cloth, which reveals the mirror. The shrouded figure attacks the living until the cloth is yanked off, which banishes the formless spirit.

Disable DC 43 Thievery (master) to steal the cloth before the spirit manifests, or DC 47 Athletics to pull the cloth off the spirit after it manifests

AC 40; Fort +26, Ref +32, Will +35
HP 230 (BT 115) spirit; Resistances all damage 20 (except force, ghost touch, spirit, or vitality; double resistance vs. non-magical)

Don Shroud (occult)
Trigger A creature enters the area

Effect The spirit steps out of the mirror, wearing the cloth as a shroud and revealing the mirror. The triggering creature is Frightened 3 unless they succeed at a DC 38 Will save. The haunt then rolls initiative.
Melee Shrouded Touch +33, Damage 3d12+19 force
Routine (3 actions) The spirit uses 3 actions to Step, fly 60 feet, or Strike, in any order. On a successful Strike the spirit's target is Frightened 1, and on a critical success, the target is Frightened 2.
Reset The haunt is reset when the mirror is covered again.
Pathfinder Dark Archive (Remastered)ORC