Golems are magical constructs. Their operation is very mana-intensiv, especially for golems made of dense materials, such as stone. Since their movements break the material they're made of, they usually banish the parts that would hinder their movement and summon those where they need to stretch. Therein lies the reason for the high mana costs.
For comparision, to power a stone golem for one hour its mana batteries need to be charged for two months.
Ami's need for an army clashes violently with her dislike in putting others in harms way which made her turn to golems as an alternative. After various experiments she didn't come to a satisfying conclusion the high mana costs and her desire for an easily replacable fighting force.
She started experimenting with ice-based golems but still couldn't get the results she desired.
After acquiring warlock minions she handed parts of her research on ice golems to them and had them come up with a solution. Due to the need for complete conjuration of the golems without any extra parts they chose to develop a complicated spell. It entailed a golem based on her designs, incorporating a mind impressed with her fighting experience and self-image as a Keeper, to allow the spell to work. 
If the hull of an ice golem is broken, it will reseal automatically and redistribute water from its inner reservoir to make up for the loss of matter. Since there will be no new water conjured in the process, the self-repairing abilities will lead to a gradual diminishment in the size of the golem. Though this still allows it to regrow completely lost limbs.
Inside the golem will float a controlling ice crystal holding the spell and anchoring the personality construct to the body. Its removal will permanently deactivate the ice golem.
An active organic dungeon heart is necessary for the spell to work since the ice golems animating intelligence is derived from the imp reation spell and thus needs the spark of life inherent in the organic hearts design. Due to time restraints Ami stored the spell in her dungeon heart to make reduce its cast time to nearly instantaneous.
Usually Ami uses mostly senshi magic for the creation her ice golems with only a bit of dungeon heart magic necessary to animate the magical constructs. However, when she has exhausted her senshi mana pool the dungeon hearts mana pool will provide the necessary magical energy. Since this is channel through an inherently evil way the created ice golem will reflect that.
A corrupted ice golem will appear to be made of obsidian, jagged edged, instead of the usual smooth ice. The finger end in claws, horns protrude from the head, the spine shows spikes and fangs poke out its mouth.