Complex sentence: After he releases them, the Avengers become suspicious of him after hearing they are wanted and they cannot remember what happened at the castle and go there, however nearly all of them are paralyzed by Nefaria's gas.
Split into simpler sentences: After he releases them, the Avengers become suspicious of him after hearing they are wanted and they cannot remember what happened at the castle. They go to the castle, however nearly all of them are paralyzed by Nefaria's gas.