Complex sentence: The Defenders is the name of a number of Marvel Comics superhero groups which are usually presented as a "non-team" of individualistic "outsiders", each known for following their own agendas.
Split into simpler sentences: The Defenders is the name of a number of fictional superhero groups appearing in American comic books published by Marvel Comics. These are usually presented as a "non-team" of individualistic "outsiders", each known for following their own agendas.