The 55th Alphic Hydras are an elite and well-respected Tempestus Scions regiment of the Ordo Tempestus that possesses a sterling reputation for having fought alongside several companies of the Ultramarines Space Marine Chapter. They are held in such high regard by the Chapter that they have been allowed to set up training facilities on multiple worlds throughout the Segmentum Ultima.
The 55th Alphic Hydras are one of the most well-respected Militarum Tempestus regiments in the Imperium. This is in part because of the number of missions that they have fought alongside the Ultramarines -- to date they have made planetfall alongside the 2nd, 5th, 7th and 8th companies over their illustrious career. So close is the association between these Scions and the Space Marines that the Alphic Hydras have recently been permitted additional training grounds throughout the Ultramar sub-sector. Some within the Ordo Tempestus whisper that some of the regiment's best young Scions have even been recruited by the Adeptus Astartes and are now Initiates of the Chapter.
The Scions of the 55th Alphic Hydras first went to war alongside the Sons of Guilliman on the Agri-World of Masali, where they aided the Ultramarines in purging the planet of Orks. Tempestor Prime Vallius Delt steered his regiment through the impassable Masali poison jungles and the vine-thorn deeps, around the flanks of a vast Greenskin mob, which they then funnelled right into the heart of an Ultramarines trap - bringing an end to the invasion with swift brutality. Chaplain Trajan of the Ultramarines 2nd Company observed that these humans fought with discipline, nobility and profound loyalty to the Ultramarines' orders, and it took little discussion for other Space Marines in the Chapter to recognise the value of the Scions.
Before long the 55th Alphic Hydras were making repeated planetfalls with the Adeptus Astartes, at the Ultramarines' request. Their most recent success was a battle upon the Crone World of ldzyk II, where they formed a stealth unit to ambush and disable an Eldar Wraithknight, turning the tide of battle in favour of the Ultramarines.
The regimental symbol of the 55th Alphic Hydras has a twofold meaning. Firstly, it echoes a sigil form the Dark Age of Technology that has been linked to the Hydras ever since their inception. Yet it also harks back to Mount Charas, where the 55th maintain their training facilities.
- Codex: Militarum Tempestus (6th Edition), pp. 21, 56