I'm really struggling with C10. It feels like I should be able to beat it with Gremory, but things just keep happening. Basically, since I have no way in hell of beating the F1 combo shield, I end up having to burn actives to keep shielding until it goes away. Then there are very few opportunities to safely stall without a heart cross, so, if I don't skyfall some hearts, I am screwed into using more actives. THEN Goemon has a resolve, so I need a board with hearts and a few dark not to hit his resolve. If I do check his resolve, things get much harder, as then he takes double damage. THEN #2, frickn' dark absorb on Zaerog.
I'm pretty confident that, hypothetically, if I ever got to Vishnu, I could probably 3-shot kill him with active, heartcross, match of 3. But that does not seem to be in the cards.
Over on reddit, somebody mentioned that they could do it with Minerva, which I tried, but couldn't get through Hera. I suppose I need to stall for a delay on floor one, then delay Hera, then stall somewhere else to delay Vishnu.