Magic Resistance. The tsochar has advantage on saving throws against spells and other magical effects.

Flesh Stealer. The tsochar disappears into a humanoid within 5 feet of it. This process takes 1 interrupted minute to complete. The humanoid must be Small, Medium or Large in size, must be alive, and must either be incapacitated or willing. Once the tsochar has entered the host's body, the tsochar can choose whether to leave its host alive (see the Inhabit ability) or destroy them from the inside and use the dead shell of a body as a vessel (see the Replace ability).

A tsochar can abandon a body it has inhabited by using an action that deals 3d6 (11) points of necrotic damage to the host. A tsochar can be forced to abandon the body by a dispel evil and good  or greater restoration spell, though the host still takes the aforementioned amount of damage. A carefully worded wish spell can banish the creature from the body without dealing damage to the host.

Inhabit. The tsochar leaves its victim alive and aware. The tsochar can take no physical actions while inhabiting a host, but it can use purely mental actions (such as communicating with its host by means of telepathy and threatening the host unless the host does as the monster wishes). When the host takes damage other than damage the tsochar inflicts on it, the inhabiting tsochar takes half that damage. A tsochar's resistances and immunities apply to both the tsochar and the host. A tsochar inhabiting a humanoid’s body feeds on the creature’s blood and tissues, dealing 1d3 points of Constitution damage per day. A host's successful DC 15 Constitution save reduces this damage by half. Tsochari are clever enough to direct their hosts to acquire curative magic to keep themselves alive indefinitely, if the situation calls for it.

Replace. The tsochar bores out the victim’s nervous system, killing the victim. It then animates the body, effectively acting as the nervous system of the dead host. The body remains alive, hosting the tsochar. This functions like a polymorph spell into the victim’s exact form, except that the tsochar can remain in the victim’s form for up to a year, and it leaves the victim’s corpse behind when it chooses to end the effect. The tsochar uses the victim’s physical ability scores in place of its own, as described by polymorph. The tsochar can remain in this form indefinitely, but once it abandons the form, it cannot reanimate the body. Tsochari that have replaced a humanoid slowly devour their new shell from the inside out. A replaced body takes 1d4 points of Constitution damage per month, which can be restored only by magical means. A successful DC 15 Constitution saving throw reduces this damage by half. Naturally, tsochari imposters choose to abandon bodies they have replaced before they become too weak to be serviceable.

Multiattack. The tsochar can use any three attacks on its turn, but can use its Constrict and Inject Poison attacks only once each per turn.

Tentacle Lash. Melee Weapon Attack: +7 to hit, range 10 ft., one target. Hit: 8 (1d10 + 4) slashing damage. On a hit, the creature must make a DC 13 Strength saving throw or be grappled by the tsochar's tentacles. While the creature is grappled in this way, it is restrained. The creature can make the Strength saving throw at the end of its next turn.

Constrict. The tsochar squeezes its tentacles around a creature it has grappled. The creature takes 2d8 (9) points of bludgeoning damage.

Inject Poison. The tsochar injects a weakening poison into a creature it has grappled. The creature is poisoned until the end of its next turn, and must make a DC 15 Constitution saving throw; on a fail, the creature's Strength ability score is reduced by 1d4 points. This Strength damage heals naturally after a short or long rest.

Internal Agony. As an action, the tsochar inflicts 1d6 (4) to 6d6 (21) points of psychic damage to the creature whose body it inhabits. It can choose how much damage to deal with this attack. The inhabited creature must succeed on a DC 15 Constitution saving throw or be incapacitated by the pain (as paralyzed) for 2d4 rounds.