One Step From Eden

The list of different spell focuses is as follows:

You need to have one card of each in your playthrough deck for this to pop.

If you play with Saffron, the starting character, she has the following in her Default starting deck:

Anima, Kinesys, Slashfik

Meaning you'll need to grab at least one of each of the following with Saffron as they pop up as you clear rooms:

Convergence
Doublelift
Glimmer
Hearth
Hexawan
Miseri
Phalanx

So, at miminum, with incredible luck, 7 room clears.
But don't worry about it too much, play through, try not to select the same focus if trying to knock this out specifically as you clear rooms.
You can also stop by the shops and (press start) and see what spells the shopkeeper is selling.

Alternatively, from their starting kits, I think the only ones with more are Violette and the Shopkeeper, so can try this with them if you unlock either of them first, Violette has in her Doubletime starting deck:

Miseri, Phalanx, Anima, Convergence

And the Shopkeeper has:

Convergence, Kinesys, Phalanx, Slashfik

You can use Angel Mode and unlock achievements. (in the Main Menu options)
There's two separate toggles, one for reducing damage taken, and one for reducing enemy speed.
The available level of that increases by 2% each death/failed run, up to a maximum of 50% reduction of each.