Arcane Leech

Amorphous. The Arcane Leech can move through a space as narrow as 1 inch wide without squeezing.

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

Power Surge. The arcane leech can absorb and store magical energy through some of its abilities. In this state, the energy is called a power surge. The leech can hold up to 3 power surges at any given time. If it would gain more, it instead regains 9 (2d8) hit points. If it has all of its hit points, it instead gains 14 (2d8 + 5) temporary hit points.

Once per turn when it deals damage to a creature or object with an attack, the leech can spend power surges to deal an extra 10 force damage to that target for every surge spent this way.

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

Multiattack. The Arcane Leech makes two Claws or Arcane Bolt attacks.

Silencing Claws. Melee Spell Attack: +9 to hit, reach 5 ft., one target. Hit: 11 (2d10) force damage. The target must succeed on a DC 17 Constitution saving throw, or be unable to speak or produce sounds for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Arcane Bolt. Ranged Spell Attack: +9 to hit, range 300 ft., one target. Hit: 14 (4d6) force damage. 

Disrupt Magic (Recharge 5-6). The arcane leech pulls at and absorbs magical energy in a 10-foot radius sphere centered on itself, creating one of the following effects:

• Mass Dispel. The Leech casts Dispel Magic on up to 5 targets within the area. Its spellcasting ability is Wisdom. The leech gains a power surge for every effect dispelled this way.
• Magic Drain. Creatures in the area must make a Constitution saving throw against DC 17. On a failure, a creature suffers 13 (3d8) necrotic damage. It can freely spend any number of spell slots to reduce this damage by 1d8 per slot level. This damage can't be reduced by any other means. On a success, it suffers no damage. The leech gains a power surge for every failed saving throw against this effect.
• Arcane Annulment. The area becomes an antimagic field (as per the spell) until the end of the leech's next turn.

Arcane Displacement. The arcane leech teleports to a point it can see within 30 ft.

Arcane Counter. When the arcane leech sees a creature casting a spell, teleporting, or using a magical ability within 60 feet of it, it can use its reaction to try to magically foil it. The creature must succeed on a Wisdom saving throw against DC 17, or its spell, teleport or magical ability fails and is wasted and the leech gains a power surge.