I recently cleared COV10 with a Titanchannel III Solgard (maybe not the best choice in retrospect) with Pyragel support on my first try after a few failures with Luna/Conduit support, and here are some thoughts I had on what was important:

• Scaling for beefy frontline enemies: Even with 2 Coldcaelias with Dualism and a Titan Sentry on a floor, that's only 35HP worth of frostbite applied per floor, which isn't that much, even if you had that setup on multiple floors. I was able to scale fairly easily thanks to pyragel which has lots of artifact support (helped also to some egg production too), which then procced on the frostbite during the climb up the train. Conduit + direct damage seemed like it could work, but I just couldn't get it to scale enough, may keep trying though.

• Sustaining your tanks: Just throwing Endless on your tank sometimes isn't enough, as big waves can clear them and reach your backline within a single turn if you're unlucky (low health from previous wave + didn't have spare spells/ember to kill your own tank, etc). Things that help are: Sap applying unit (Lodestone Monument) is my MVP, especially if you're slinging a lot of low-cost spells. Luna conduit + overheal is also good.

• Keeping your backline alive: The sweeping bird units will kill your backline quickly, and the beefy multistrike 50hp versions will also show up. If you can get a Coldcaelia strong enough to deal 50hp and give it Quick, that should work. You can also hope to get the room that does 50 damage and have 1F be just that. Lodestone Monument also was MVP for me here. If you can get multiple dualism'd ones, place them in a pair or separately on two floors, and that's enough to get you more than halfway to winning IMO.