Complex sentence: His magical abilities are in the use of the two-headed staff he carries at all times, but beyond that he is entirely helpless, both on land and (surprisingly, since he appears to be some sort of frog or toad) in the water.
Split into simpler sentences: His magical abilities are in the use of the two-headed staff he is charged with carrying. Beyond that he is entirely helpless, both on land and (surprisingly, since he appears to be some sort of frog or toad) in the water.