I doubt the direct approach casting magic at the darkness barrier will work much, unfortunately.

...It is quite possible that using teleportation could allow an access point through the barrier. But, the question is how to keep such an access point, regardless of how it's created, open long enough to take the barrier down, or to make any headway against Maleficent's stronghold on the castle.

[A pause.]

Perhaps we should request another meeting with others, much as the Fire Lord did before the invasion.