have refill all spellcard at wave 5 10 15 20 gain reward after wave 5 and gain more when more than wave 5
#20 wave battle
frigid cloak
winter tartan
This is an interesting idea, I suggest adding something like this into Daily Arena as a new kind of challenge for big hands, with extra rewards - more Superior Incense and Burners. 
static juniper
Can't wait to see some YouTuber clear it with one stall unit in 5000 turns
winter tartan
Yep I'm afraid the content about Spell Cards refilling for each 5 turns is too op with somebody since it's easy to find holes in that to exploit countless loops. It should be increased to 10 turns if we want to make a real challenge, after all, those things can be calculated later if the team decides to make something like this.
frigid cloak
Yep I'm afraid the content about Spell Cards refilling for each 5 turns is too o...
added diffculty to make it harder
winter tartan
If it's Phantasm, so yes. Because, when each 5 turns all the Spell Cards are refilled, so if the true difficulty level is just Lunatic, the run is still easy to get pass for an Extra difficulty level. We should add something like Gauges or Binds with turn 5 10 15 20 if we want to make a real challenge, but it will cost more brain cells lifespans to build all of them for Daily Arena, maybe Weekly Extra will be better to choose. 
digital frigate
Take away refills, make waves never ending, option to continue at current spot with fresh units. Similar to tower, but each wave is RNG. Characters revive when starting again from wave 1.
winter tartan
This one is a nice idea too. But beside that, if we want an endless battle, instead of waves, I think we should put everything in 1 single wave, then resurrect the enemies, or just swap them with other available teams rotationally after defeating all of them and make them stronger than before, increase Gauges, Barriers, stats, whatever to a certain limit. Of course put it with Phantasm difficulty level, to make an Extra challenge for big hands. It's way easier than building 10 or 20 waves, or make a loop with a long run, especially for a weekly or even daily content. 
And still, I wish I won't see anything like a long scrolling UI for units selection like one we have with the Tower. 