This mod has a bunch of necessary bosses, and these ones on the image are not even the half of them! In total, ToFL adds 11 necessary bosses, and 5 side ones. All of the bosses are unique in their own way, and they all will surprise you one way or another.
ToFL adds a bunch of utilities to help you find/fight bosses, make your life easier, or even read minds of entities! Almost all of the new items/tools have some new gimmick - dash, shoot projectiles, etc. All of the new equipment is tied to the bosses, so defeating them will feel rewarding and exciting!
This mod adds a whole new build system - Marvs. Each marv has different effect and can be passive/active.
Some essential gimmicks like dash, double jump or dive are contained within marvs, and to get their effects you need new equipment - marv storage. You can get only one storage per player, and its capacity increases with your progression in the mod. However, if you install too much marvs in your storage, you will get overmarvelled and have a bunch of debuffs, which would be the last thing you will want.
ToFL adds a bunch of misc. stuff, such as soul gathering mechanic, 2 new biomes, more than 40 new mobs, abundance of building blocks and items with variable uses. Try it yourself!