Soul Gem (Skyrim)

Soul Gems are used for enchanting weapons and armor at an Arcane Enchanter or recharging previously enchanted weapons. After using a soul gem (with the exclusion of Azura's Star and The Black Star) it is destroyed.

Mining
In Blackreach, the Dwemer underground realm, there are Geode ore deposits. These drop soul gems of random values ranging from petty to black soul gems. They tend to follow the leveled algorithm.

Purchasing
Filled and empty soul gems can be purchased from merchants directly. Filled gems are three to four times the price of an empty one.

Dungeon loot

 * In Dwemer ruins, most Dwarven Automatons drop soul gems, ranging from Petty to Grand gems.
 * Vampire Lairs (Note: In vampire lairs Black Soul Gems might also be found.)
 * Nordic ruins
 * There are also a number of soul gems that can be found at The College of Winterhold, most of which cannot be taken without Stealing. Becoming Arch-Mage revokes this crime, unless the Soul Gems are owned by an NPC.
 * During a quest for Drevis Neloren, 1-3 free, empty Soul Gems of any size can be obtained.
 * Several unmarked locations on the world map.

Soul trapping
Trapping souls in Soul Gems requires the Conjuration spell Soul trap or a Soul Trap enchantment. Killing an enemy with the spell cast upon them or using the enchantment draws their soul into one gem of the appropriate size. If no gem of the appropriate size or greater exists in the inventory, the soul is lost. An example of a weapon enchanted with the ability to capture souls is the Mace of Molag Bal.

Bound weapons
Bound weapons such as Bound Sword or Bound Bow can automatically soul trap attacked enemies if the Conjuration Perk, "Soul Stealer", has been learned.

Soul size
Soul size is determined by enemy type. Generally, smaller or lower-leveled creatures possess Lesser, Petty, and Common souls, such as Foxes, Falmer, or Chaurus. Larger or higher leveled creatures possess Greater and Grand souls, such as the Mammoth (Grand) or Giants (Greater).

Humanoid races (Men or Mer) possess Grand souls, but can only be trapped in a Black Soul Gem or the Daedric artifact Black Star, which is obtained through the quest of the same name. Falmer and Draugr are an exception, as their souls may be captured by standard gems.

Types
Soul gems are separated into types based on the capacity they can carry. The soul gem types are petty, lesser, common, greater, grand and black.

Souls
The following are creatures that give souls:

Petty Souls: Alpha Wolf, Chicken, Cow, Deer, Dog, Draugr, Elk, Fox, Goat, Mudcrab, Rabbit, Skeever, Skeleton, Wisp, Wolf

Lesser Souls: Bear, Chaurus, Draugr Wright, Falmer, Falmer Skulker, Flame Atronach, Giant Frostbite Spider, Horse, Ice Wolf, Ice Wraith, Restless Draugr, Sabre Cat, Spriggan, Troll, Werewolf, Wounded Frostbite Spider

Common Souls: Cave Bear, Chaurus Reaper, Curalmil, Draugr Deathlord, Draugr Overlord, Draugr Scourge, Draugr Scourge Lord, Gloomlurker, Nightprowler, Shadowmaster, Frost Atronach, Frost Troll, Hagraven, Snow Bear, Spriggan Matron, Udefrykte

Greater Souls: Draugr Death Overlord, Draugr Deathlord, Giant, The Pale Lady, Storm Atronach, Wispmother

Grand Souls: Dragon Priest, Draugr Death Overlord, Draugr Deathlord, Falmer Shadowmaster, Guardian Saerek, Guardian Torsten, Mammoth

Black Soul Gems
Black Soul Gems can be used for gathering humanoid souls such as:
 * NPCs (A character, not necessarily hostile, from any of the 10 playable races)
 * Apprentice Fire Mage
 * Bandits
 * Forsworn
 * Ice Mage
 * Necromage
 * Necromancer
 * Pyromancer
 * Storm Mage
 * Vampires

Falmer and Giants do not count as humanoids, they are considered creatures.

Black Soul Gems can be filled with creature souls. This could waste the gem by filling it with a soul that is not rated Grand. Dropping the gem on the floor and picking it back up will make it "empty" again.

Trivia

 * If a soul of a small size has been trapped in a large soul gem, the gem can be dropped and then picked up. The gem will then be empty.
 * Stolen charged soul gems cannot be used to recharge magical weapons.
 * The Black Soul Gem will retain any trapped soul if dropped. (So be careful when harvesting!!!)
 * The Mammoths appear to be the most reliable source of Grand souls. Otherwise, Grand souls are only dropped by the toughest boss-level dungeon monsters (which are usually limited to 1 per dungeon, and only at higher levels), such as the Draugr Death Overlord, boss-level Falmer Shadowmaster, or Dragon Priest.