Legendary Expertise. All d20 rolls, except for hit dice, the aathronec makes have advantage.

Legendary Heritage. All d20 rolls, except for hit dice, made within a 200ft. radius of the aathronec that are not made by the aathronec or any creature it summoned have disadvantage. If the aathronec is incapacitated, stunned or unconscious Legendary Heritage does nothing.

Ranks from the Opportunity. If the aathronec or a creature it summoned kills a player, the aathronec may decide to turn the dead player's body become aathrospawns. If it does, 1d6 of them are created within 5ft. of the dead player. Each of them makes an action when they are summoned. All decisions any aathrospawn makes is considered the decision of the aathronec. If the player is revived for any reason, the aathrospawns that came from them meld back into that player. If the aathronec dies, all aathrospawns it created are destroyed, unless every aathrospawn that was created from a certain character are still alive, in which all instances of that: each of those aathrospawns meld back into that player. That player is revived unconscious and at 0 hit points.

Whenever a player melds back from aathrospawns they are prone and stunned for one round. 

Multiattack. The aathronec can use Claw, Tail and one of the following: Brutalise the Mind; Frightful Presence; or Harrowing Desire on each of its turns. 

Claw. Melee Weapon Attack: +11 to hit, reach 15ft., up to two targets. Hit: 28 (4d8 + 4) slashing damage.

Tail. Melee Weapon Attack: +9 to hit, reach 20ft., up to two targets. Hit: 24 (4d6+3) bludgeoning damage. If the target is a creature, it must succeed on a DC 18 Strength saving throw or be knocked prone.

Brutalise the Mind. Ranged Spell Attack: +18 to hit, reach 50ft., one target. Hit: (6d8 + 10) psychic damage. If the target succeeds on a DC 22 Charisma saving throw they can negate this damage.

Frightful Presence. Each creature of the aathronec's choice within 120 feet of it and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the aathronec is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the aathronec's Frightful Presence for the next 24 hours.

Harrowing Desire. Up to three creatures of the aathonec's choice within 70ft. of it must succeed on a DC 16 Intelligence saving throw or become stunned for 1 minute. A creature can repeat the saving throw as a bonus action or an action on each of its turns, ending the effect on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the aathronec's Harrowing Desire for the next 2 rounds. During that creature's turn, the aathronec makes its decisions. It can only one action/bonus action and not the other. If it does use an action or bonus action, its other action/bonus action must be used to repeat the saving throw. Using an action is considered a legendary action. When the effect ends, the controlled player is stunned for 1 minute.

The aathronec can take 4 legendary actions, choosing from the options below. Up to two legendary actions can be used at a time and only at the end of another creature's turn, unless it is Control. The aathronec regains spent legendary actions at the start of its turn.

Attack. The aathronec makes one claw attack or tail attack.

Move. The aathronec moves up to half its speed.

Control. The a may make an action as a player that is under its Harrowing Desire (bonus actions and movement do not require a legendary action.)

Torment. Any creature under the aathronec's Harrowing Desire takes 7 (3d4) psychic damage.