He'll look back at Sif and then the castle with a frown. "I-I know a good few spells but aside from that. I can't wrap my head around this barrier. M-Maybe a certain type of magic can dispel it. Something not as d-direct then?"

He'll hold open his palm then, green eyes glowing as electric sparks dance across his hand. He'll flick his wrist and send a bolt of lighting off towards the barrier. Hopefully this might help, hopefully.