Cone of cold, dominate person, Bigsby's hand: 3 spell slots

Disintegrate: 2 spell slots

Blink, Fireball, lightning bolt: 4 spell slots

As an action the summoner may open a gate that deploys 1d4 imps each turn that he can control on his turn.

Once the portal is open, the summoner may use an action to use any of the spells at his disposal

The acolyte summoner may use a reaction to cast either the shield or absorb elements spells