Carnival Phantasm exists to let Fate/Tsukihime fans watch their favorite characters completely unhinged, freed from any narrative obligation to make sense. Caren's scheme to buy the world, Phantas-Moon getting a theatrical release, Shiki's romance arc that refuses to end, these aren't jokes with setup and punchline, they're pure character chaos. The whole thing costs nothing to describe and everything to experience if you've lived in these worlds long enough to recognize how fundamentally wrong everything is allowed to go.
Carnival Phantasm gets a bonus comedy episode in this supernatural OVA, released only on DVD alongside the special edition Take Moon volume. Caren Ortensia tries to take over the world with money, and her results are mixed. Phantas-Moon sees her television show turned into a movie. Shiki, meanwhile, is caught up in a romance whose story plays out over the course of years.