Idea: Castable arrows

Make an Arrow Cast like you would anything else, put in your favorite molten stuff, and enjoy! Then each arrow could have custom stats that play into the bow's base stats, and maybe even have custom effects!

Slime arrows definitely need to bounce off of targets

Edit: ALSO, a Molten Quiver! Keep your favorite molten stuff in a quiver, dip the arrow in it, and then you can have two effects at once!