Completed at the start of Episode 1:
Earth + Fire = Lava
Air + Lava = Stone
I've created a video including all the achievements for this game including a Google Sheets help system to guide you through it to save time. If you don't want to do that there is a whole list broken down as needed.
Credit to Mike Marcelais & RadicalSniper99 for the original list.
Check out:
Thanks :)