The major antagonists of From Software games usually have a lot of shared history. Some are blood relatives, some are lovers, some are enemies with grudges stretching back centuries. A few are all these things simultaneously. But they seldom meet, reconcile or thrash out their differences in-game. By the time we encounter them as players they've become monstrous hermits, isolated and corrupted by their vast ambitions and desires.
Some bossfights do, however, let you summon an ally character from your enemy's past, perhaps to fulfil one of each game's hidden sidequests. A select group of modders have taken this concept further. They've hacked the game to pit bosses against each other, dropping them into each other's arenas and filming the results in first-person. It's a feat of bloody fan service which exposes the nuances of each boss's design.
Garden of Eyes has been making From Software's bosses murder each other since the days of Bloodborne. His first video put the game's mentor figure Gehrman and Lady Maria, coverstar for the Old Hunters DLC, up against Laurence, first Vicar of the infamous Healing Church. It's not a close match. Laurence has the reach, but Gehrman and Maria have the speed and finesse, though Laurence's second phase - in which he tears himself apart to spew lava everywhere - at least denies the pair a spectacular finish.