Virthad

Trigger The doppelganger is transformed with Change Shape and another creature moves adjacent to it or takes a hostile action against it. Effect The doppelganger reverts to its natural form and can make a Strike against the triggering creature. If the creature was unaware the doppelganger was in disguise, that creature is Off-Guard against this attack.

The doppelganger takes on the specific appearance of any Small or Medium humanoid who it has seen and whose appearance it remembers. This doesn't change the doppelganger's Speed or its attack and damage bonuses with its Strikes but might change the damage type its Strikes deal (typically to bludgeoning). The monster changes its shape indefinitely. It can use this action again to return to its natural shape or adopt a new shape. Unless otherwise noted, a monster cannot use Change Shape to appear as a specific individual. Using Change Shape counts as creating a disguise for the Impersonate use of Deception. The monster's transformation automatically defeats Perception DCs to determine whether the creature is a member of the ancestry or creature type into which it transformed, and it gains a +4 status bonus to its Deception DC to prevent others from seeing through its disguise. Change Shape abilities specify what shapes the monster can adopt. The monster doesn't gain any special abilities of the new shape, only its physical form. For example, in each shape, it replaces its normal Speeds and Strikes, and might potentially change its senses or size. Any changes are listed in its stat block.

Requirements Virthad is carrying a sack of prepared flytrap pods

Virthad dumps the contents of the sack into two adjacent squares while invoking prayers to Lamashtu. The pods grow into two elite Snapping Flytraps that immediately attack any non-worshipper of Lamashtu they can detect.