To dream of being immortal represents feelings about never having to lose or be witnessed losing. Positively, it may reflect feelings of permanent supremacy over competitive or opposition. Situations where you or someone else feels all powerful. A reputation for winning that can never be outdone. Achievements that seem impossible to outdo.
Negatively, it may reflect feelings about showing off your supremacy to people you don’t like. It could also reflect feelings about how awful it is to experience an enemy being too powerful or a problem being permanent. Feeling annoyed by someone who never loses.
Alternatively, from a negative perspective being immortal may reflect a naive belief in once’s self being imperious to defeat or weakness. Arrogance that overlooks it’s weaknesses. An ignorant belief in one’s self never confronting objective reality because it seems too far off in the future. Flagrant short-term showing off at the expensive long-term winning. Stupidly believing you are the best there is and the best there ever will be.