Elemental stones

Aeketh
Andrion (red)

Bloodstone
Glabrezu (red)
Firedrake (red)

Castle Medievia
Guardian Elementals (gray/blue/red/clear)
Water Weird (blue)

Cliffs of Berkovic
Each area earth, fire, etc has a minor mob that loads its color (red/blue/gray/clear)

Dark Woods
Mistlings (clear)
Wraths (clear)

Den of the Necromancer
Elementals (red)

Derah (good)
Elemental (blue)

Eldricht'ss Tomb
Gargoyles (gray)

Enchanted Oak Graveyard
Nymphs (blue)
Spirits (clear)

Fire Giants Keep
Firenewts (red)
Hydras (red)

G'dangus
Fireflies (red)
Faecula (grey)

Lagoon
Golem (red)

Lattyrna
Watery Doubles (blue)

New Ashton
Tendril Demon? (red)

Raskins Valley
Jellyfish(blue)

Ryvaera
Princess (blue)

Sceptrum Ishachi
Elementals (gray/blue/red/clear)

Spire of Kirys Ayr
Stone Golem (gray)

Spirited Heights and Horneg's
Water Sprites (blue)
Gargoyles (gray)
Elementals (gray/blue/red/clear)
Guardians of Shadows (clear)
Gneiss (gray)
Homunculus
Astral Guardian (clear)

Temple of Kukdheuda
Djavul (red)

Thanos
High Priest (blue)

Vatos
Fire Elementals (red)

Xanthal

Can also be purchased in a Vanlarra shop for 5k gold plus eggs

SUPERS- (requires 4 colored elementals, gold, essence)
EARTH/WARRIOR/GRAY-Tharhalas(griffon)
FIRE/MAGE/RED-Chepstow, Bloodstone(Glabrezu)
WATER/CLERIC/BLUE-Alps, Casti
AIR/THIEF/CLEAR-Kukdheuda(skeleton)