I can't quite understand the difference difference between "senmorta" and "senmortulo".
From what I understood the first would apply to anything that might be immortal, example; "la senmorta principo" or "La korpo estas mortema, la animo estas senmorta". The second applies directly and necessarily to a person, when refering to someone that is (or supposedly is) imortal, example "unu nura senmortulo" or "Urbo de la Senmortuloj".
Is this the right meaning of these words?
Additional info: I want to use this as an title or epitet of a character, like "Mateso, la Senmortulo", which could be simply called "Senmortulo" or "La senmortulo", similarly to how Superman is also called "The Man of Steel".