If this is not related to a CTF, "Theseus" frequently appears in these technical contexts:
An open repository for theses and publications from Finnish Universities of Applied Sciences. UNIX secure server - Theseus Theseus.rar
Use the file command to confirm it is actually a RAR archive and not a renamed file. If this is not related to a CTF,
Run exiftool Theseus.rar to see if the creator left hints in the comments or creation timestamps. Theseus.rar
Extract a "flag" (a hidden string like THM{...} or HTB{...} ) from the archive. 🛠️ Common Solving Steps