Ethereal Jaunt. As a bonus action, the Yanlani trapper can magically shift from the Material Plane to the Ethereal Plane, or vice versa.

Shapechanger. The Yanlani trapper can use its action to polymorph into an object or back into its true, chimeric form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It cannot take any attack actions while in object form other than the mimic bite attack action.  It reverts to its true form if it dies.

False Appearance (Object Form Only). While the Yanlani trapper remains motionless, it is indistinguishable from an ordinary object.

Petrifying Gaze. If a creature starts its turn within 30 feet of the Yanlani trapper and the two of them can see each other, the Yanlani trapper can force the creature to make a DC 15 Constitution saving throw if the Yanlani trapper isn't incapacitated. On a failed save, the creature magically begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or other magic.

A creature that isn't surprised can avert its eyes to avoid the saving throw at the start of its turn. If it does so, it can't see the Yanlani trapper until the start of its next turn, when it can avert its eyes again.

If it looks at the Yanlani trapper in the meantime, it must immediately make the save. If the Yanlani trapper sees its reflection within 30 feet of it in bright light, it mistakes itself for a rival and targets itself with its gaze.

Multiattack. The Yanlani trapper makes three attacks: one with its basilisk head, one with its phase spider head, and one with its mimic head.

Basilisk Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage plus 7 (2d6) poison damage.

Mimic Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target.  Hit: 8 (1d8 + 4) piercing damage plus 4 (1d8) acid damage.

Phase Spider Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target.  Hit: 9 (1d10 + 4) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 18 (4d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.