It is the higher level equivalent to Soul Shard, and as such replaces Soul Shards in the crafting of the top 3 Adventure Materials; Undead Ash, Life Force, and Alien Cell. 10 Soul Gems are needed to create 1 Soul Forge, which is needed to create the Rank-A fusion swords of the above 3 materials.
You can also use 6 Soul Gems to recharge 1 use of the Soul Hammer and its consequent upgraded versions.
You can randomly obtain Soul Gem from the following locations:
- Flaming Volcano: Ifrit(2nd Boss)
- Polar Glacier: Beauty Under the Moon(2nd Boss), Doom Beast(3rd Boss)
- Imperial Tomb: Incineration Site(#4 on the map), Underground Secret Chamber(#7), Undead Dragon(Rare Enemy), Eternal Life Form(1st Boss), Undead King(3rd Boss)
- Canyon of Immortality: Spiritual Vein(#4 on the map), Water Spring of Tranquility(#7), Monument of Souls(#15), Ascended Immortal(1st Boss), Shura(2nd Boss)
- Dragon Archipelago: Buried Treasure(#4 on the map), Primitive Dragon Stone(#7), Dragonian(Rare Enemy), Kaiser Dragon(1st Boss), Tiamat(2nd Boss)
- Abyssal Sea: Forlorn Monastery(#4 on the map), Shrine of the Sea Ruler(#7), Will-devouring Tree(#11), Kraken(1st Boss), Leviathan(2nd Boss), Abyssal Nightmare(3rd Boss)
- Impact Site: Shattered Meteor(#8 on the map), Nutrient Storage(#14), Grandmother(1st Boss), Ender(2nd Boss), Manhunter(3rd Boss)
- Hellgate: Graveyard of Braves(#4 on the map), Village of Demonic Weaponary(#7), Sunless Hill(#9), Deman Lord(1st Boss), Majin(2nd Boss), Deman of Thousand Swords(3rd Boss)
- Skyland: Shining Cliff(#3 on the map), Pool of Angelic Feathers(#6), Training Post(#10), Mental Training Ground(#13 on the map), Six Winged Angel, Divine Dragon, Guardian
- Pandemonium: Gargoyle's Hidden Stash(#4 on the map), Hidden Stairway(#7), Calamity Furnace(#13), Death(1st Boss), Sin (2nd Boss), Apocalypse (3rd Boss)