I got all the way to level 15 on Rare. My 3* fully ascended and leveled team was Jahangir, GanJu, Greymane, Belith, Renfeld, but not that order. Renfeld with 5 emblems, the rest except Jahangir (who has no emblems) with 6 emblems.
I only have one Epic hero, Scarlett. But not allowed on the Rare level. Bomb attacks? bzzzzt Verboten! My cadre of one 4* and the rest 3* Troops. Can’t use them either. I’d been dumping every troop found or summoned into upgrades. So I did some grinding on the map to scrounge up a selection of 2* troops (except 1* red and still haven’t been given any new yellow)
The 14 levels weren’t too difficult. I had to keep crafting a ton of the basic healing potions (20 of them can go further than 5 better ones) basic mana and basic antidotes. 10 each vs 5. Also axe attacks. IIRc for about the first half of the stages I didn’t have to use any battle items. The boards were good with plenty of green for Belith. I did burn 75 gems a couple of times in the second half to finish off the bosses.
But 15? Forget it. I tried several times, wasted another 75 gems once. Green was practically nonexistent, or they’d dogpile Belith to take her out first thing. I tried hitting the bosses with all five axe attacks right away, which would knock their health down quite a bit.
But then every time, the one that casts the total invulnerability would do that and it would give me no green for Belith, or she’d be gone. Utterly fruitless pummeling until the invulnerability would run out (or if it’d give me green and Belith was still around to dispel) and I could get just one or two hits in before Mr. Invulnerable was recharged to cast it again. What made it worse was one of the bosses apparently had some continuous health recharge spell for the team so even when I did get them beat down around 50%, once they started tossing spells it was me defeated with the bosses back to full health.
If I’d had a full slate of fully leveled up 2* troops and at least one other hero with dispel like Belith the 15th stage may have been beatable with the limits on heroes, troops, and battle items.
What was really irritating, mainly because of the lack of creativity, was the monsters with reflection were ONLY BLUE. Jeeze, how about some variety? Make the reflection ones different color each wave. But nope, blue, every stage and almost every level.
I also tried the other two levels. Got to the 4th on the middle before hitting the wall. Just did the first stage on the highest. My “reward”? ONE summon token. I would’ve received the same just for doing the first Rare stage and no more, and saved a bunch of gems. That’s all I did on a couple others of these events for the same reward.