Complex sentence: In 2011 comics, Namor joined the mutant superhero team the X-Men and helped with the Curse of the Mutants and Avengers vs. X-Men events before joining the Illuminati and All-New Invaders.
Split into simpler sentences: In 2011 comics, Namor joined the mutant superhero team the X-Men. Namor helped with the Curse of the Mutants, and Avengers vs. X-Men events, before joining the Illuminati, and All-New Invaders.