Which of these is a term used for an often-repeated character or idea that can be the same as the theme?

Leitmotif.

Explanation:

Leitmotif is a German word meaning "guiding motif" or a brief reiterating musical phrase affiliated to the particular character or idea. It is the salient recurring figure that is introduced to convey a significant message. Such a motif has to maintain its identity in constant modified( in rhythm, harmony) appearances. These motifs are introduced to add to the coherence of work and assist the author to relate the work to the audience more effectively and introduce a special element to the work.

bro we need more information. how are we supposed to answer this?

the answer is:

magna carta