Binding Ricochet. Adar can cast spells through his Conjured Creatures rather than himself. 

Glyphic Scholar. Adar can read, write, and speak any elemental language, and can sense if an elemental is within 300ft of him, knowing its precise location and direction.

Conjuror. Adar Valkov (Magniacra) is a 12th-level spellcaster. His spellcasting ability is Sanity (spell save DC 17, +10 to hit with spell attacks). Adar Valkov has following Conjuror spells prepared:
Cantrips (at will): [produce flame], [toll the dead], [mage hand]
1st level (4 slots): [cause fear], [thunderwave], [witch bolt], [arms of Hadar] 

2nd level (3 slots): [pass without a trace], [flaming sphere], [web]

3rd level (3 slots): [dispel magic], [remove curse], [fireball]

4th level (3 slots): [banishment], [blight], [polymorph]

5th level (2 slots): [bigby's hand], [infinite bombardment], [legend lore]

6th level (1 slot): [arcane gate]

Dagger. Melee Weapon Attack: +3 to hit, reach 5 ft., # target. Hit: # (1d4 + 3) [piercing] damage. 

Call Forth (3/Long Rest). Adar calls upon the Conjuror's Grimoire to summon an elemental force from one of the planes of primal magic. Choose either Dangerous Summon or Familiar Summon.

Familiar Summon. Adar summons one of the following creatures for one minute, until the creature drops to 0 hit points, or if Adar becomes incapacitated: Fire Elemental, Air Elemental, Water Elemental, Earth Elemental, Xorn, Salamander, Invisible Stalker.

Dangerous Summon. Adar summons one of the following creatures for one minute, until the creature drops to 0 hit points, or if Adar becomes incapacitated: Air Elemental Myrmidon, Earth Elemental Myrmidon, Fire Elemental Myrmidon, Water Elemental Myrmidon, Tlexolotl, Frost Salamander, Arclight Pheonix. Adar must make a Sanity Saving throw (+9) at the beginning of each of his turns. The DC begins at 10 on the first turn the creature is summoned, and increases by 1 each time the save is repeated. If the save fails, the creature remains but begins to attack Adar, and his allies. 

Elemental Chaos (Recharge 6). Adar gains 3d6 temp hit points, and tiny elementals swarm in a 15ft radius around him. Hostile creatures that start their turn or enter the radius for the first time must make a SAN saving throw, DC 17, or take 3d6 damage matching the elemental Adar has conjured most recently, half as much on a successful save. This radius effect drops when he loses his temp hit points, or after one minute. 

Enter the description for how bonus actions work for your monster here.

Revoke (2/Long Rest). Adar cancels the casting of one spell he can see being cast if he makes a successful Arcana check (DC 15). He must drop concentration on a spell or expend his highest available spell slot to revoke the spell.