With future perfect (F2) you jump to a point in the future, turn round and say some action is finished then. Actually a complicated thing and cumbersome and in most cases you can express the same idea much simpler without using F2. This tense existed in Latin and it was imitated by writers.
In current English usage, muse can refer in general to a person who inspires an artist, writer, or musician.
Definition of imagine for English Language Learners. : 1  to think of or create (something that is not real) in your mind. : 2  to form a picture or idea in your mind of (something that is not real or present) : 3  to have or form (an idea or opinion that is not accurate or based on reality)