[7245,1407,6348,7245,3076,1,2,3,3,1,1,1,14025]
A fast straightforward team.
Frost Lizard creates blue gems which are useful for the hero and Sapphirax.
If you don’t have 2 x Sapphirax replace one with Frostfeather. His magic stats quickly increase via Sapphirax’s third trait.
[7245,1407,6348,6724,3076,1,2,3,3,1,1,1,14025]
Both of these teams quickly beat E12 in all kingdoms so will be good to the final boss.
It has been a while since I have done Underspire, what is the minimum purchase each day to make sure one reach the final rewards?
I go with 1500 gems in total, split into 3x all 3 offers and 4x only 2 offers. In case you’re afraid of overspending, split into 3,3,2,2,2,2,3.
My brother uses this method of buying torches 2,2,2,3,3,3 and whatever is needed on Sunday.
He also uncovers the entire map and plays all sentinel rooms. That way he finishes around 140 total rooms, give or take with a few free torches.
2 packs per day has always been enough with bunch to spare for treasure rooms (but not for full clear).
If you only care about boss rooms, you can manage with smaller amount (for example, do 2,2,2,2 for 600 gems, see where you are on Thursday and proceed from there with 50 gem packs). It depends on how lucky you are with rooms and how much risk you’re willing to take.
Thanks for the good feedback everyone. It is obvious, but also a solid option to buy all 3 on Sunday if you feel you need some more for the last day, @Dust_Angel.
So far, I’ve always managed to complete it with at most two purchases each day. My usual approach is two purchases Monday to Friday inclusive, last two days based on how close I’m likely to the end. Hunting for sentinels requires extra purchases.
I also purchase 2 packs per day Monday-Friday, and see where I am Saturday. I ignore treasure rooms during the week and wait until I finished all the bosses. I usually end up just buying 2 packs on Sat/Sun so I can clear the treasure rooms I already uncovered.
Same. Has only failed me once – “failed” as in “buy all 3 torch packs on Sunday but fall just short of reaching the final room” – but oof, that one burned. I’ve started to get more of a feel now for whether I need the 3rd pack on Saturday.
Last week I have 155 rooms, such numbers occur approximately once every two months 
I haven’t assembled my Underspire team yet, but I am partial to leading with Borealis because why not? Better Skull tank than Sapphirax and that third trait synergizes with Borealis’s own spellcast quite nicely.
My approach to Underspire is similar to @Voq 's, with the exception that I hit the Sentinel rooms as I find them rather than saving them for the end of the week. It makes little practical difference, but I get Torches often enough to please me and it’s also easier for me than trying to go back and find them later.
(This is why my notes include where I found a Sentinel battle and not just rarity and reward.)
As for my team this week? I’m using my go-to Fey/Glacial Peaks PvP team, actually:
Ice Sapphire (Frostmage)
Daughter of Time
King of Ravens
Daughter of Ice
Banner: Umbral Nexus, although Lyrasza’s Lair would also work. (+purple/yellow, -brown)
Ice Sapphire is better than the new exploder because it summons an Ice Storm as part of its’ affixes. The idea is simply to loop over and over again, using the Daughter of Time to create Hourglass gems and having either the Hero or the Raven King pop them while exploding the board.
It’s a bit slow, but it’s very reliable and loop-y once it gets going.
