What is caspien magic ability?
It's worth noting that I veer more 'fantasy' than romantasy when I write, so there are definitely 'magicians' or wizardly types out there.
Casp is not a Seer, but instead a proper, honest to goodness mage that was privately trained in the Autumn Court (Beron's not letting out that his sickly son is actually as powerful as he is and prefers barbed jabs about him in company). He is second to only Eris as heir in terms of his power and control over his flames, but he's an accomplished spellweaver as well.
If you're into D&D, think of him as an evoker, though it's a little more complicated than that. His powers skew elemental and destructive: fire and lightning and thunder, beads of force that can be shaped to act as magical wrecking balls, caustic acids, calling down flaming rocks from the sky, that kind of thing. The trade-off is that he's absolute trash at the magic of *creation*, so shielding doesn't come as easily nor do spells that heal or mend.
Hopefully this additional info helps! It's worth noting that he doesn't ALWAYS look as exhausted and wrecked as he does on the picture I drew of him. When he calls upon a LOT of magic though, it feeds off of his energy and life force, weakening him the more he burns (lol) through his spells. When he stops, his magical healing takes over and he slowly goes back to normal. You can bet Beron's tested where the edges of his magic are, though, and that he's wandered out of the training rings looking much older and more frail than he is many, many times.