Without proper context, I'm going to assume "this guy" is Clan Boss? 1M damage in one day will eventually become absolutely effortless for you. That's the amount of damage I can do in one turn. The fact that you are struggling to reach that amount over the course of the fight likely means your understanding of the mechanics of the fight are the root cause of your problems. Why don't you post your roster / team that you use against him? Perhaps we can help clarify some things.

As for when the day starts - there are two moments, actually. At 8PM EST / Midnight UTC, the quests reset, along with most other content (Doom Tower, Faction Wars, etc...). At something around 6AM EST / 10AM UTC (I'm not sure the exact time since I'm asleep usually), Clan Boss resets. Around that same time, weekly arena resets occur.

Well, I meant Demon Lord, sorry about that.

As of now my strongest toons are Elhain, Warmaiden, Warpriest, Dhampir, Galek, and Shaman; all but the last 2 are 50 (the last two are 40) and all are maxed on Rank and fully Ascended. I have a lot of other Rares that I'm working on Leveling; the best I've got at the moment is High Khatun and I just got Huntress via Fragment Summon. My own Level at the moment is 40. I'm working on Leveling Heriess and Spirithost; someone online said those were good for beginners.

Okay. So there are quite a few problems here to address:

• Clan Boss is designed for teams of full level 60 champs, all with full masteries, all fully ascended, and all fully booked on their important abilities. Running with anything less is a problem. Running with the team you have is a major problem. Focus on getting Elhain to 60, so she can help you farm food to level other champs.
• Warpriest, Dhampir, and Shaman are all trash champs. Don't waste any more resources on them. It's unfortunate you brought Warpriest to 50, but what's done is done. Don't bring Galek or Shaman past 40. Eventually, upgrade Galek to 5* and then feed him to someone as food. Leave Shaman at 40 so she can be used with a dupe as a Faction Guardian, and, eventually, when you have the Orc Guardian Hall filled, you'll be able to turn her into food too.
• Khatun is great, definitely worth bringing to 60. Huntress on the other hand is trash. Leave her as-is, potentially eventually using her for the fusion she's involved in.
• Be extremely diligent about which champs you plan on leveling. You've already demonstrated some questionable decisions. I'd highly recommend in the future that you post your decisions of who you intend to level before you do so, to avoid leveling the wrong champs.

I see most of the points, but to be fair, Dhampir is pretty good with Spider Queen. Come to think of it, I always found it odd I was getting even THAT much use out of an uncommon.

Thanks. I'm guessing my big problem is trying this too early. Lol