Downed Body. An [monster name] will refer to their disguised form as their host form. while in their true form. Due to this, they can leave a decoy of their 'host' laying around to trick people whom question it about their origins by making a deception check. If someone inspects the body they may roll perception or investigation check higher than the deception rolled.

Changed Heart. As an action, you can transform your appearance or revert to your natural form. Unlike changeling, you have no choice over your reverted form and once your disguised form is chosen cannot be manipulated without a disguise kit which is destroyed after use. You revert to your natural form if you die.

Unsettling Visage. When a creature you can see makes an attack roll against you, you can use your reaction to impose disadvantage on the roll. You must use this feature before knowing whether the attack hits or misses.

Using this trait reveals your shapeshifting nature to any creature within 30 feet that can see you. You will remain this way for 1d6 turns with a penalty of -10 speed for turns above 4. Once you use this trait, you can’t use it again until you finish a short or long rest. You will also be  out for 1d3 turns afterwards

Spellcasting. The [monster name] acts two levels above the host form but do not hold the upgraded health. If they are a spell caster, this is also changed to match. They know only one cantrip and one 1st level spell from the hosts main list. If the host holds a book with spells in it they may utilise these.

They also know Telepathy at 1st level.

Paradise In Parallel. Utilising telepathy, the creature can make one chosen target (Unwilling or willing) to have their mind warped to see something different, often a paradise. If the target is unwilling, they must make a wisdom or will save. If they pass, they cannot fall for it again until a long rest has occurred. If succeeded or willing the target becomes incapacitated and cannot move. The effect wears off after 1d5 turns.

Siege Monster: The {monster name} deals double damage to objects and structures.

Bite: Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) piercing damage. If the target is a creature, it must succeed on a DC 11 strength saving throw or be knocked prone.

Claw: Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) slashing damage.