Betilivatis "Bet"

Blastwave. If Bet hits with her first attack, roll a d20 for each monster standing next to the monster she hit. If a roll is 10 or above, Bet deals 1d4 point(s) of fire damage to that monster as well.

Spellcasting.  Bet is a 3rd-level spellcaster. Her spellcasting ability is intelligence (spell save DC 14, +6 to hit with spell attacks). Bet has following wizard spells prepared:
Cantrips (at will): Fire Bolt, Dancing Lights, Control Flames
1st level (4): Catapult, Feather Fall, Magic Missile, Shield
2st level (3): Dragon's Breath, Maximilian’s Earthen Grasp
3st level (2): Slow, Blink

Quarterstaff. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 3 (1d6) bludgeoning damage.

Opportunity Attack. You can make an opportunity attack when a hostile creature that you can see moves out of your reach. To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach.