Iron Crypticle

Using different weapon and scroll types will first require you to unlock that many. Unfortunately, the game gives you no indication of what unlocks new weapons and scrolls. You'll just notice that after each run, you will unlock some number of new things. I'm not sure if it's cumulative challenges, getting to certain points, one-off challenges, etc. I just know that I unlocked stuff pretty regularly, and then unlocked a huge amount of things the first time I beat a New Game run, and by the time I was playing NG+ I had enough of each for this achievement. I therefore think it's sufficient to say that the required amount of unlocks will come naturally while playing this game. Weapons are easier since you can touch them and then trigger and overwrite your existing weapon, so you'll constantly be going through new weapons. With scrolls, you need to make it a point to actually use them so you can pick up another one. I always forgot to use them, so whenever I would get a scroll drop and couldn't pick it up (since I already had one), I'd use my current scroll and grab the new one. In this way, I unlocked this achievement relatively early.