Adjective for 'being able to use magic' or 'being able to cast spells'
I propose thaumaturgic, derived from thaumaturge, a 'worker of wonders or miracles; magician' according to dictionary.com.
Alternatively, sorcerous, 'of the nature of, or involving, sorcery'.
The closest word I can think of is "magical", which would be "possesses magical properties"; that seems a little off, however. You could try describing them as a noun (Kreuvf is a wizard/sorcerer/mage/magician).
If you really want something that functions as an adjective, though, magic-capable or spellcast-capable sound like they should work.