Originally Posted by
Gormon
It is a grand soul-gem that can be re-used (ie when used you get an empty black star in your inventory). It can only be used to absorb humanoid souls (ie not creatures).
due to a bug, the black star is capable of catching any soul atm, they will prob fix it in some patch so it the way you described, and the way it is meant to be.
@McBurger:
trap souls of your enemies via a weapon that has soul trap enchantment or with a soul trap spell.
Once the black star has a soul in it (it will not say empty but most likely grand in its name - due to a bug it can contain lesser souls than grand (humanoid souls are all grand) atm) go to an enchanting platform (lot of them in Skyrim, I use the one in Mages guild the most.
Pick an item, pick an enchantment (to learn an enchantment u must get an item with the desired enchantment and disenchant it, u will learn the enchant and the item will disappear) and use the black start to make the item.
The star will be empty end ready for catching a new soul. Grand souls get you the most from your enchantments as does your enchanting skill.
Like this u can make equipment like Gorman has showed on previous page.