An Iron Golem-shaped mob with curved arms and a crystal cube for a head. They are hostile and spawn semi-commonly in The Snare dimension. They have 80 health and do 8 damage.
The Crystalline Guardian has a random gem (usually either a sapphire, topaz, or ruby, but rarely a diamond) as an eye, which it drops upon death.
Crystalline Guardians are immune to fire. They are used to make automatic gemstone farms.