Weave Eater

Anti-Magic. Resistant to all types of magic, vulnerable to physical attacks.

Counterspell Ability. The Weave Eater can cast varying levels of the spell Counterspell at will. Roll 1d8 for each Weave Eater encountered to determine the max level their counterspells reach. Then, roll 1d4 to determine how many counterspells they have for each level from 1 to that initial d8 rolled number.

Cantrip Canceling. Cantrips are counterspelled completely when cast within a 15ft radius of a Weave Eater.

The Weave Eater makes 2 actions per round, Counterspell does not count towards these actions.

Counterspell. Use one of the set counterspell slots from the Counterspell Ability trait. This can happen instantly as a spellcaster is trying to cast a spell.

Bite. Melee Weapon Attack: +6 to hit, reach 10 ft., 1 target. Hit: 29 (3d12 + 8) [magical piercing] damage. 

Crystal Spew. Ranged Weapon Attack: +5 to hit, range 10/60 ft., 2 targets. Hit: 22 (4d6 + 9) [magical bludgeoning] damage. Stun. When a creature is hit with a Crystal Spew attack, they must make a DC 19 Constitution Saving Throw or be stunned on a failed save until the Weave Eater's next turn.

Eat Crystals. As a bonus action, if the Weave Eater is within 10ft of an Anti-Magic Crystal, it can spend its bonus action eating more crystals and regain one counterspell ability slot. To determine this slot, roll 1d8 and add 1 to that level of counterspell ability.