D&D 5E Suggest a monster

[Voadam]

Perhaps an allip (Mordenkainen’s Tome of Foes, pg. 116)

While more of a minion, you could also use bookkeepers (Kobold Press Creature Codex, pg. 55)

Another could be a Manastorm golem (Creature Codex, pg. 203), with some minor revisions.

Beat me to the manastorm golem. Medium sized is a rarity for constructs.

From Fifth Edition Foes there is the CR 9 furnace golem which could work if it is a fireball type wizard, but it is size large by default.

Tome of Horrors has a CR 5 medium sized ice golem with a recharging cold breath weapon that could be reskinned to be a spell.

Mostly anything with a ranged attack can be reskinned to be a caster type.

 

[jayoungr]

Thanks for your suggestions, everyone!

Someone pointed me to the Painted Phantasm (CR 7) in Tome of Foes 3, so I wound up using that (actually, two of them) for this encounter. But my party is going to be infiltrating a wizards' stronghold soon, so I expect to need more spellcasting foes soon, and you've given me a lot to work with.