Counterflux Overcast (Recharge 5–6).

The blastseeker can create an additional effect immediately after casting a spell. Roll a d6 to determine the effect:

1–3. The blastseeker creates a 15-foot-radius invisible sphere centered on itself that lasts until the end of its next turn. Creatures in the sphere have disadvantage on saving throws against spells and other magical effects.
4–6. The blastseeker creates a 15-foot-radius invisible sphere centered on itself that lasts until the end of its next turn. Creatures in the sphere have advantage on saving throws against spells and other magical effects.

Innate Spellcasting.

The blastseeker's innate spellcasting ability is Intelligence (spell save DC 14, +6 to hit with spell attacks). The blastseeker can innately cast the following spells, requiring no components other than its Izzet gear, which doesn't function for others:

3/day each: enlarge/reduce, mage armor (self only), scorching ray
1/day each: counterspell, dispel magic, protection from energy

Actions

Rapier.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage.

Counterflux Blastseeker