Recycled Combat is a modpack based off of old and/or unused mods. This has tons of adventure packed into it. You can visit Middle Earth, go to a tropical paradise, visit the Aether, and much much more. There are a lot of items and ways to buff them in this mod, and different weapon choices. While there is technically an end because of the Ender Dragon, there really isn't and you can defeat the bosses in (almost) any order. It's a pretty straightforward modpack (although I need to add in achievements which will take a while).
Update 2.0 Massive update; added more mods to strive to make it kinda sorta like Terraria. Just keep an open mind whilst going through this mod and you'll be fine. I will (hopefully) add Craft Tweaker with some new recipes coded for some modded weapons and stuff; just need to figure out how to code it in the first place.