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I like to keep Soul Gems due to the fact they sell. And also pays off if you have enchanted weapons.

My thing is to enchant armor. Cause they don't require a charge. Weapons just give me trouble. But In case I do need one I have a staff that soul traps and weapon that is enchanted.

Ancient Ghost Common
NPC (any race) Black
Ancient Sanctified Dead Common
Ogre >=GreaterL:-3
Azhklan Troll leveledL:+0
Painted Troll leveledL:+0
Benirus Manor Ghost leveledL:-1
Rat Petty
Black Bear Common
Sanctified Ancient Spectre leveled
Boar Lesser
Sanctified Dead <=LesserL:-1
Brown Bear Greater
Savage Goblin leveledL:+0
Clannfear Common
Savage Minotaur leveledL:+0
Clannfear Runt Lesser
Savage Ogre leveledL:+1
Daedroth Greater
Savage Troll leveledL:+0
Dark Guardian leveledL:+0
Scamp Lesser
Deer Petty
Sheep Petty
Deranged Zombie leveled
Skeleton Petty
Dog Petty
Skeleton Champion Greater
Dread Zombie Greater
Skeleton Guardian Lesser
Dremora Black
Skeleton Hero Common
Everscamp Lesser
Slaughterfish Petty
Faded Wraith Common
Spectral Sailor >=LesserL:+1
Flame Atronach Common
Spider Daedra Greater
Frost Atronach Greater
Spriggan Common
Ghost <=LesserL:-1
Storm Atronach Greater
Gloom Wraith GrandL:-3
Stunted Scamp Petty
Goblin Petty
Swamp Troll leveledL:+0
Goblin Berserker Common
Timber Wolf Lesser
Goblin Shaman Greater
Tribe Goblin Berserker leveledL:+1
Goblin Skirmisher Lesser
Tribe Goblin Farmer leveledL:-3
Goblin Warlord Grand
Tribe Goblin Guard leveledL:-1
Headless Zombie Common
Tribe Goblin Shaman >=LesserL:+0
Horse Lesser
Tribe Goblin Skirmisher leveledL:+0
Imp <=LesserL:-1
Tribe Goblin War Chief leveledL:+2
Kalperklan Troll leveledL:+0
Troll Lesser
Land Dreugh Greater
Undead Akaviri Soldier leveledL:-1
Lich Grand
Vampire Black
Minotaur Common
Will-o-the-Wisp Common
Minotaur Lord Grand
Wraith Greater
Minotaur of the Grove leveledL:+0
Wolf Petty
Mountain Lion Common
Xivilai Grand
Mud Crab Petty
Zombie Lesser
Nether Lich >=GreaterL:-7

CREATING BLACK SOUL GEMS:
^^ This can be founded out during hte Nacromancers Moon Quest: But Rather I found this out on my own.

The locations are: Dark Fissure (east from the shrine of Vaermina)
Fort Istirus (east of Kvatch)
Fort Linchal (northeast of Kvatch)
Wendelbek (at the headwaters of the Panther River).
Outside each of these locations, you will find a white altar draped in a red cloth

During the hours of 12am-12 am Put an Empty Grand Soul Gem in the alter, the 8th day of the last time you have seen the Light from heaven, otherwords called the Shade of the Revenant. This happens every 8 days in the game. You may have to wait a long time til you see light shooting from the alter.

Next you have to put in more than one Grand Soul gem, during this time after you throw a few in there, you must have a soul trap spell.

When you open the alter agin there should be an empty Black soul Gem in there. Repeat if desired. But the soul trap only works once per stone. So Enjoy. These can be used to trap, NPCs, Vampires, and Dremora.

A word of warning: I don't know what the crime is for studying nacromancy so you better not talk to anyone from the mages guild or NPC's while in possession of one. If you can remember the Recommendation from that joker with the Ring of Burden. They didn't like it one bit, when they discovered their Guild leader was using them.

Grand Soul Gems that are stolen WILL have it's status removed if it changes to Black. sweatdrop

That's all well and good for you, but not everyone has the Guide.

This I imagine is extremely useful for all the mages, etc. out there. Personally though, I prefer to use my good 'ol Daedric short sword. I do have enchanted items, but I find that most of the enchantments I need can be bought. *Shrug* I just fail to see the point of enchanting, as it's no longer a skill.