Sounds interesting, let's see... there's so much to choose from...

Toad: Applies a debuff, turning enemies in a small and wide frontal cone into toads for 15 seconds.
Source: Zuro Roggo (The Antitower), Halicarnassus (Deltascape V3.0)

The Classical Elements - Rotate between casting Fire Orbs, Thin Ice, Downburst, and Levinbolt while channeling.
Fire orbs: Creates several smaller fire orbs that expands after a few seconds then explode dealing aoe damage for maybe 130 potency each.
Thin Ice: Covers the ground with a slippery ice floor in a 15y radius for a short time.
Downburst: Pushes surrounding enemies and Fire Orbs away from you.
Levinbolt: Applies a lightning aoe to each enemy in 15y radius.
Cast type: Channeling
Total cast time: 8-10s
Source: Alte Roite (Deltascape V1.0)

Dispose: Fires beams of light in a 45 degree medium frontal cone for 220 potency, then rotates character ca. 35 degrees and removes a Wind Up stack. Repeats until all Wind Up stacks are used up.
Additional effect: If no Wind Up stack is in effect, tapping the spell button before it finishes to cast applies a Wind Up stack for each tap.
Wind Up: Increases potency by 10 for each stack with a maximum of 8. One stack lasts for about 2 seconds.
Source: Construct 7 (The Ridorana Lighthouse)

They might not work, but it was interesting to think of...