Gem Girl

Evolution
A final evolution of a Rock Spirit. They can be evolved from Rock Golems if they have a HP gene of 0.

They can be evolved into four different types:

These Elites have a very difficult requirement for evolution: a HP gene of 0. Even if you skip the reshaping process for a stronger base spirit, this becomes increasingly harder over time as genes values in portals grow and your Main Character spawns stronger spirits with higher Magic. Since final spirit evolutions are rare, you can't rely on one appearing in a cave portal or showing up in the tavern hire list to recruit.

If you wish to use them it's advised to evolve two of them right from the start of the game in order to overcome the low genes via breeding. However the trouble is worth it.

Combat
Gem Girls have incredible potential as tanks, surpassing even Spiked Seals thanks to their unmatched 3.0 HP growth, Regenerating onTurnStart and DrainMana onAttack to maintain it. Beyond that, they also get high growths across most of their stats and powerful spells, allowing them to excel in multiple roles.

However, note that their base HP is low and their armor slot has been replaced with a misc slot, making them fragile at first.