During the Carrionite-Hervoken war, when the Eternals banished the Carrionites to the Deep Darkness, Morrígan managed to avoid being banished with the others. Because while they were at war with the Hervoken, she left; fleeing both the war and the Hervoken by heading to the other end of the universe, using a pocketful of ship tickets. And she was a good way away when they banished the Carrionites. Ever since then, she's being doing her own thing, with the aid of a few, carefully hidden, words.
Morrígan is quick-witted and sly, and deceitful. She's not immoral though, and does what she believes is right. She thinks that slipping under the radar makes life easier. She hopes to break her people out again someday.