D20 and AEI... What is AEI you're asking (and you're probably wondering what D20 is as well for that matter because, unless you're kind of a nerd, you won't know). Well, AEI is short for something I like to call "Ass Eating Instruction"... Which I happen to be a rather staunch fan of. Here, I give some pointers on how I like it. As for D20... Well, that's not really important.