Only register an item if a dependancy is loaded

How would I make an item only appear if another mod is present? I want to make enchantment runes that are an early game alternative to enchanting, but I dont want to have hundreds of useless items in the creative menu / jei that can't be crafter without a mod. I cant figure out how I would add support for other enchantment mods without making a seperate mod that depends on it. Thanks :)