Wow, thanks! Glad to hear you enjoyed it. I used GameMaker Studio 2 - I'm not sure if I would recommend it, but it's what I'm most familiar with. Yes, there are multiple endings - if you go to the far east and west you might discover them.
If you're fine with spoilers - one is where you get all 7 gems and ascend, in one you climb the wall on the left, and in the third one you get the Rod and take the souls of all other NPCs. (I'm thinking of decreasing it to maybe half of the creatures though, to make it easier for players to stumble into).