Cadmean Citadel
The Cadmean Citadel (referred to by some as Structure 132[2b]) was a fortress located on the planet Hydra Cordatus.[1a][2a]
Overview
The Citadel was no mere armoured redoubt - the structure's walls were formed from a stone not native to the planet and incorporated ancient technology unknown to the Mechanicum.[1a][2b] This allowed the Citadel to repair breaches in its walls without outside intervention, and even reshape the walls to actively defend itself. It could create spiked outcroppings to impale attackers or open voids in its structure before refilling them, entombing an attacker in solid rock.[1a] Some even compared the Citadel's ability to heal and defend itself to a living creature.[1a][2b]
History
After Hydra Cordatus was brought into compliance during the Great Crusade, the Cadmean Citadel became the seat of the planet's Imperial government.[1a]
Early in the Horus Heresy, Hydra Cordatus was invaded by the Iron Warriors.[1a][2a] The world's Imperial defenders, including a company of the Imperial Fists Legion led by Captain Felix Cassander, holed themselves up in the Cadmean Citadel.[1a][1b] Ultimately, however, the Iron Warriors overcame the Citadel's defences and it fell.[1b][1c] Warsmith Harkor's battalion was the first to breach the Citadel. However, because Harkor had acted against Perturabo's orders, the Primarch censured him and stripped him of his rank.[1b]
In the aftermath of the invasion, Warsmith Falk vowed that one day, after Horus' rebellion, he would return to Hydra Cordatus and rebuild the Citadel.[1c]
