Arcanophage

Magic Resistance. The Arcanophage has advantage on saving throws against spells and other magical effects.

Pack Tactics. Gains advantage on attacks when another Arcanophage is threatening target creature.

Multi-Attack. May make 2 Claw attacks per turn

Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., 1 target. Hit: 3 (1d4 + 1) Slashing damage. 

Action Ranged Attack. RangedWeapon Attack: +# to hit, range #/# ft., # target. Hit: # (#d# + #) [damage type] damage.

Magical Frenzy.  The Arcanophage is drawn towards sources of magic.  When a spell is cast within 15 feet of the Arcanophage it can use its reaction to move up to its speed toward the creature that cast the spell and make an attack against the creature.  This movement does not provoke opportunity attacks.

Absorb Magic.  As a reaction when the arcanophage is targeted by a spell attack roll a d6.  1-3 the attack goes through unhindered.  4-6 the Arcanophage gains temporary HP equal to half the splls damage, before applying resistance or immunity.  Recharge this ability on a 5-6.

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

Legendary Action Name (Costs # Actions). Enter the description for your legendary action.