In an age when mobile games are too easy, there is still one last hope for a challenging/frustrating experience. Yes, I speak of roguelike games. Nothing increases the tension like perma-death. There's plenty of that in Heroes Of Loot 2 from OrangePixel. It also has wizards, dungeons, valkyries, and lots of monsters.
As you can probably tell from the name, Heroes Of Loot 2 is the sequel to Heroes Of Loot. That game was well-reviewed, and this one looks like a competent continuation of that. Since it's a roguelike game, you have retro graphics, randomly-generated levels, and perma-death. You can unlock new abilities to aid you in future runs, but death otherwise sends you back to zero.
A nice twist to the dungeon crawler formula is that Heroes Of Loot 2 invites you to choose both a ranged and melee character. You can switch between them at will as the situation warrants. Oh, and there are no in-app purchases. Simply pay $2.49 and it's all yours. That's a 50% off promo price, though.