Groot is an extraterrestrial tree monster who initially came to Earth seeking humans to capture and study. Groot was seemingly destroyed by termites used by Leslie Evans.
Xemnu made a duplicate of Groot that was used to fight the Hulk but it was destroyed in the battle.
Groot was later revealed to have survived, but was a captive of the Collector and held in his zoo in Canada until Groot and the other captive creatures were freed by the Mole Man. Groot and the other creatures rampaged in New York City until they were stopped by a band of superheroes, and were then dumped through a portal to the Negative Zone.