How is it useful, because it summons enemies? Can it do anything else?
the Atronach Forge, located in The Midden, under the College of Winterhold has a number of recipes beyond summoning hostile Atronach/Dremora.
Variations on the summoning recipe can give you scrolls, spell tomes, or staffs that will summon friendly atronachs. (As well as recipes for creating the elemental salts needed for the atronach recipes.
Additionally, the forge can 'upgrade' unenchanted ebony armour/weapons into their daedric counterparts. Or even create a random piece of daedric equipment with a random enchantment from scratch. Both without needing the otherwise prerequisite smithing perk (Although you will likely need that perk to better improve the equipment afterwards).