The .rar extension indicates this is a compressed archive. Depending on where you found it, it could be:
The game features cooperative multiplayer for up to four players and an arena mode for boss fights. Developer: Black Tower Studios. File Context Obcidian.Legacy.rar
Files meant to modify the game or associated tools. Obcidian.Legacy.rar
The file likely contains files related to Obcidian Legacy (often corrected to Obsidian Legacy ), an isometric Action RPG (ARPG) that was originally available on PC via Steam in Early Access. About the Game Genre: Indie Action RPG with an "arcadey" feel. Obcidian.Legacy.rar
An archived version of the game client or assets.