I did this one relatively recently. In fact, I actually knocked it out on my first delve attempt after the previous campaign artifact bonus went away!
My team: Sledgepaw to tank, two Hex Rats after him, Rattigar to bring up the rear. I chose to ignore the Plague Rat because I didn’t want to chance the explosions leaving a terrific board for the AI – especially the possibility to whack me with skulls a couple of times. (I place a higher value on board control than I do on the Plague Rat generating mana.)
Banner: +2 Brown/+1 Purple (don’t remember the minus). The idea being to fill the Hex Rats as quickly as possible.
Hoard: Somewhere around the 240-260 level; I can pull a number off my console later if that really matters. Kingdom Power Level 15, so 50% bonus on top of that.
(EDIT: Hoard 259. That seems to be one of my “lucky” numbers, although it’s expensive as hell to get Hoards that high.)
Pathing: There isn’t a single Tier V room I’d want to go through. There are very few Tier IV rooms I’d go through – Dragon Hatchery (with Dragon Soul, not Venbarak) and Coral Caverns are probably the only two I’d attempt. So most of my runs – including the successful one at the end – went counter-clockwise around the outside through the II - III - II - III route. Mildly dangerous on account of giving the AI a lot of chances to wreck your run, but easier because Tier II and Tier III rooms are manageable once your hoard gives you some level of statistical parity.
Strategy: Try and fill Sledgepaw and both Hex Rats at the same time. Use Sledgepaw to drop Curse and Stun on the lead unit, then plonk that lead unit with the Hex Rats. If casting the Rattigar drops Curse on an enemy, plonk it with a Hex Rat as well if possible.
Prioritize skulls when possible. If there isn’t a skull match, preference should be Brown - Purple - Yellow - Green. The last two can be reversed if you so desire; Rattigar is a useful unit albeit one with unpredictable targeting.
You don’t have healing other than Sledgepaw’s regeneration trait, so it’s a damage race. You do have to deal with status effects, especially in the mirror matches. At least one Medal of Orpheus is strongly suggested, at least in the 1st and final rooms.
Sledgepaw is handy for board control, although it can be a little unwieldy given how large the area of effect on his spell is. But your stars are probably the Hex Rats, especially when you use Sledgepaw to set them up. You let Sledgepaw tank because of his regeneration and his Armored trait; his ability to soak up some additional damage is much more valuable than using one of the other troops that inflicts Curse when dealing skull damage.
I think that covers everything that may come to mind.