Siwan would most likely have a basic bitch heal, complete with chant and glowy hands. Call it something completely original. Like Cure. Maybe the ability to form a 1x1 ft barrier of light that can block some stuff. Barrier, or something like that. Maybe a small force emanating from himself, knocking away things that are near.

Full on sorta support stuff, so I don't sling lightning around like a cracked out Zeus.