Spider Climb: The Yanii can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check

Devils Sight: Magical darkness doesn’t provoke the Yanii’s darkvision.

Legendary Resistance (3/day): If the Yanii fails an ability check, it can choose succeed instead.

Regeneration: The Yanii regains 20 hit points at the start of its turn, unless it has taken radiant damage since its last turn. The Yanii dies only if it has 0 hit points and doesn’t regenerate.

Hellish Body: The Yanii’s weapon attacks used with it’s body is magical and deals an extra 9 (2d8) necrotic damage on hit (included in the attack).

Keen Sight: The Yanii has advantage on Wisdom (Perception) checks that rely on sight.

Shapechanger: The Yanii can use it’s action to polymorph into a swarm of insects, a bat, a female drow mage or a medium cloud of dust. The Yanii regains its hit dice, hit points and Intelligence, Wisdom, and Charisma scores, as well as its languages, proficencies based on Wisdom, Charisma or Intelligence, senses, and it’s telepathy. While in dust form, the Yanii has a speed of 0ft. and a flying speed of 60ft. and got immunity to all damage, except radiant, psychic, and force. It can also occupy another creatures space and vice versa. A creature ends its turn in the same space as the cloud must succeed on a DC 20 Constitution saving throw or be blinded until the end of its next turn. It reverts to its true form if it dies.

Paralyzing Eye: A creature within 150ft. of the Yanii that can see its central eye must succeed on a DC 17 Wisdom saving throw or be paralyzed until the start of its next turn.

Siege Monster: The Yanii deals double damage to objects and structures.

Innate spellcasting: The Yanii’s spellcasting ability is Wisdom (spell save DC 26, +18 to hit on spells). It can innately cast the following spells, requiring no material components:

At will: minor illusion, fire bolt, witch bolt, hellish rebuke

5/day each: find familiar, web, scorching ray

3/day each: eyebite, invisibility (self only), vampiric touch, fireball

1/day each: power word kill, time stop, delayed blast fireball, weird

Multiattack: The Yanii makes as many attacks as it wants, but can’t attack more if it has used its action points

Action Points: The Yanii has 16 action points which it can use in any way. It regains any used action points at the start of its turn.

Frightful Presence (costs 3 action points): Every creature within 120 ft of the Yanii must succeed on a DC 22 Wisdom saving throw or be frightened and paralyzed for 1 minute. A target can repeat the saving throw at the end of its turn, with disadvantage if the Yanii is within the line of sight, ending the effect on itself on a success. A successful save makes the target immune to the Yanii for 24 hours.

Claw attack (costs 4 action points): Melee Weapon Attack: +19 to hit, reach 15ft, one target. Hit: 26 (3d10 + 10) slashing damage plus 9 (2d8) necrotic damage , and the target must succeed on a DC 20 Constitution saving throw or be stunned until the end of the Yanii’s next turn.

Bite (costs 5 action points): Melee Weapon Attack: +19 to hit, reach 15ft, one target. Hit: 42 (5d12 + 10) piercing damage plus 9 (2d8) necrotic damage, and the target isgrappled and must succeed on a DC 20 Constitution saving throw or take 26 (4d6) poison damage and be cursed. While cursed, the target’s maximum hit points will be reduced by 26 (4d6) each time it finishes a long rest. The target dies if it’s hit point maximum reduces to 0. A remove curse spell or other magic can end the curse.

Swallow (costs 12 action points): Melee Weapon attack: The Yanii bites a creature grappled by it. On hit, the target takes the bite’s damage, is swallowed, and the grapple ends. While swallowed, the target is blinded and restrained, has a total cover against attacks and other effects outside the Yanii, and takes 70 (20d6) acid damage at the start of each of the Yanii’s turns. If the Yanii dies, the target is no longer restrained, and can escape from the corpse by using 40ft of its movement, exiting prone. If the Yanii takes 80 or more damage in a single turn from a creature inside it, it must succeed on a DC 20 Constitution saving throw or regurgitate all swallowed creatures, which fall prone in a space within 10ft if the Yanii.

Tail (costs 4 action points): Melee Weapon Attack: +19 to hit, reach 25ft, one target. Hit: 55 (10d10) bludgeoning damage plus 9 (2d8) necrotic damage, and the target must succeed on a DC 22 Strength saving throw or be knocked prone.

Cast a spell (costs 3 action points): The Yanii casts a spell.

Fire Breath (costs 10 action points, recharge 5-6): The Yanii exhales fire in a 150ft. cone. Each creature in that area must make a DC 26 Dexterity saving throw, taking 90 (20d8) fire damage on a failure, or half as much on a successful one.

Hypnotizing Eye (costs 13 action points): The Yanii stares on a creature within 60ft. of it. The target must succeed on a DC 24 Charisma saving throw, or be charmed. The charmed creature has Intelligence and Charisma scores of 1 (-5), and the Yanii chooses what the target does until the start of its next turn.

Teleport (costs 9 action points): The Yanii magically teleports itself and anything it is wearing or carrying, to place within 120 feet of it. If the space was occupied, the Yanii takes 16 (3d10) force damage, and the teleportation fails.

Earthquake (costs 4 action points): An earthquake appears around the Yanii. Every creature within 150 feet of it, unless itself, must succeed on a DC 25 Strength saving throw or be knocked prone.

Dash (costs 14 action points): The Yanii uses a dash action.

Hide (costs 8 action points): The Yanii uses a hide action.

Disengage (costs 9 action points): The Yanii uses a disengage action.

Dodge (costs 11 action points): The Yanii uses a dodge action.

Help (costs 13 action points): The Yanii uses a help action.

Defence: Once each round, when a creature hits the Yanii with an attack, the Yanii may use one of its defences, chosen from the options below:

Invisible: The Yanii magically turns invisible until the start of its next turn. While invisible, it can’t use any legendary actions, reactions or actions. Anything it is wearing or carrying is invisible with it.

Teleport: The Yanii and anything it is wearing or carrying magically teleports to an unoccupied space within 60 feet of it that it can see.

Learn the attack: The Yanii learns the attack, and it’s next turn it can magically create the components needed (for example a spell material component or a weapon) and use the same attack, unless the damage from the attack included radiant. The attack will cost 10 action points, and the Yanii can only use it one time before the components turns into ash, and it forgets how to make the attack.

The Yanii has 5 legendary actions, chosen from the options below. Only one legendary action can be used at time, and only at the end of another creatures turn. The Yanii regains spent legendary actions at the end of its next turn.

Earthquake: The Yanii uses its earthquake attack.

Bite: The Yanii uses its bite attack.

Tornado of negative energy (costs 2 actions): The Yanii creates a tornado of energy from the abyss in a space within 120 feet of it. All huge or smaller creatures within 60 feet of the tornado must succeed on a DC 26 Strength saving throw or take 18 (4d8) necrotic damage and be thrown 120 feet away in a random direction. If a target hits a solid mass, it takes 3 (1d6) bludgeoning damage for every 5 feet it was thrown.

Hellish Shadow (costs 3 actions): The Yanii creates a circle of magical shadows powered with strong negative energy. Within 120 feet of the Yanii, it is magical darkness, and every creature that starts its turn in that area other than itself must make a DC 26 Wisdom saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much on a successful one. On a failure, the creature is also paralyzed until the end of its next turn. The shadow disappears after 1 round.