Chaos Spawn, Swarmlord

Legendary Resistance (3/day). If the swarmlord fails a saving throw, he can choose to succeed instead.

Malign Presence. When a creature within 60 feet of the Swarmlord casts a spell, it must expend a spell slot one level higher than the spell’s normal minimum. Cantrips require expending a 1st-level spell slot.

Psychic Barrier. The swarmlord has advantage on saving throws against spells and other magical effects.

Psychic Weapons. The swarmlord's weapon attacks are magical.

Shadow in the Warp. If a spellcaster within 60 feet of the swarmlord casts a spell, the roll a d20. On a 1, the spell fails and the slot is expended.

Multiattack. The swarmlord makes four bone sabe attacks. It can replace one attack with a use of Spellcasting to cast Shatter (level 5 version, spell save DC 19, and it deals Psychic damage instead of Thunder damage).

Bone Sabre. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 24 (4d6 + 10) slashing damage.

Sabre Parry. Trigger: The swarmlord is hit by a melee attack roll. Response: The swarmlord adds 4 to its AC against melee attack rolls (including the triggering attack) until the start of its next turn, possibly causing the attacks to miss.

The Swarmlord can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Swarmlord regains spent legendary actions at the start of his turn.

Attack. The Swarmlord makes one bone sabre attack.

Move. The Swarmlord moves up to its speed without provoking attacks of opportunity.

Paroxysm. Every enemy creature within 60 ft. of the Swarmlord must succeed on a DC 19 Wisdom saving throw or be stunned until the end of their next turn. The swarmlord can’t take this action again until the start of its next turn.