Unfortunately there's no easy solution to this: getting the achievement is going to be grindy. However, there are some things you can do to get there a bit more quickly.

Wait until you have maximum slots in your spells and robe, and Grade A materials.

Hopefully you already noticed the little message about picking materials to replace. But in case you didn't... click any material slots you don't ilke, then 'Mulligan' to reroll them. You can also reroll your artifact.




If you get a loadout that's unusable, don't bother even trying. Exit to hub and retry for a new loadout.

In my opinion, this one is THE most important: make sure you have a Philosopher's Stone in your robe. If you don't, reroll ALL the slots in your robe to try and get it. If you still don't, you should probably just quit and retry... it's THAT important.

You can sometimes get away without this if you have spells with life-steal on them, but that only works when there's critters to kill. On some bosses, there aren't, or you just take damage too fast to heal it back before dying.

You should have at least one spell that does decent damage, since you'll still need to kill the bosses. This is slightly less important on the temple levels since you only have to imprison the boss, but you still have to kill the monsters. Sometimes, you'll just get unlucky and even after a reroll all your spells will be short-ranged, teleporting/knockback, ammunition-limited, or otherwise useless.

Despite what I said in the second point, if your loadout looks interesting, give it a shot. Maybe you have a wall-piercing splitting ricochet turret with lifesteal that clears an entire screen in seconds. If you're having fun, well, isn't that the point of gaming? ;)