Just for fun, I'll dig this out of my archives...
Chapter Name: Crimson Lions
Gene Seed: Crimson Fists
Founding #: 10; 101873M35
Home-Vessel: Spelaeum Leonis
By the time of the 10th founding, the dire need for additional Space Marine chapters had already eroded any established tradition of founding on a specific day or year. Though the High Lords of Terra had envisioned the 10th founding as a return to the early tradition of founding on the first day of the millennium, necessity dictated otherwise. The founding fleets spread from Holy Terra into the winds of the Empyrean on the awkward date of 101873M35, over a century before originally envisioned, not even on Emperor’s Day.
Unfortunately, though the day was without celebrations or fanfare within the Imperium, it did not go unnoticed by the Ruinous Powers. Tipped off by heretic informants, and desirous of the vast quantities of equipment, material, and gene-seed, the Alpha Legion, led by the champion Clanaeus, cast a net for the fledgling chapters, hoping to catch one still in transit to their homeworld.
The founding fleet of the Crimson Lions made for the Rho Pardus system in the Ultima Segmentum, where they would establish their fortress monastery on Pardus Tertius, a mountainous, forested planet inhabited by hardy, primitive warrior clans. Fate dictated otherwise. Thirty-nine days out of Terra, while dropping from the warp to confirm their course at the starless nexus of Evastor, the Asp-class destroyer Cerastes encountered a squadron of traitor Contravenor-class scout ships, and though it destroyed one and damaged another, two escaped to make their reports. Commodore Vitnolo, commanding the Imperial Navy escort, and Brother-Captain Turso knew that it was only a matter of time before the main force of the enemy relocated them and attacked. Their prescience and forethought saved the fleet from the ravening maw of Chaos.
The attack finally came as they prepared to enter the warp from the Aranicus system, home to a naval logistics depot where the fleet had just taken on supplies. As the fleet raced to a viable Warp point, the Lunar-class cruiser Actius fought a desperate rearguard action against the forces of the archenemy, buying the time to transit. The flight cost them dearly, and few ships escaped without damage, limping into the shipyards of Sarconus, trailing atmosphere and debris. Many, particularly mass-freighters carrying forges and foundries, would never move under their own power again.
The Yard-Master, Arch-Magos Teoma, inadvertently suggested a solution when he claimed that the sorely damaged founding fleet looked more like a space hulk than anything from the holy forges of Mars, upon which one of his attending Navis Magos suggested constructing a hulk from the damaged mass-freighters. Historians have theorized that the only reason Teoma approved the venture was because he was sure of its failure, and wished to punish his errant subordinate, but the amalgamation of three damaged and one sound mass-freighters proved remarkably resilient. Thus, they forged the core of the Spelaeum Leonis, and it has served as the chapter's home ever since. Chapter artificers have added to it considerably in the intervening millennia, from ferrocrete armor slabs to epic gothic carvings to minor elements of trophy vessels taken by the chapter in combat.
The monastery-barge Spelaeum Leonis is as much of a homeworld as the Crimson Lions know. It has grown ever larger and capable over the centuries, but one element has never changed: its slow speed, both in real space and the Warp. The chapter selects the Master of the Fleet for a keen strategic mind, for he must analyze the surrounding sectors and recommend the best course for the Leonis, both to meet the needs of the Imperium and the chapter.
The roaming course of the monastery makes consistent recruiting difficult, though the Master of the Fleet attempts to plot courses that pass likely recruit worlds. The chapter prefers to recruit from (Imperial or Crimson Fists). The difficulty in maintaining a regular flow of aspirants has led to a slight variance in their implantation process. The chapter strives to maintain a small pool of recruits that train and receive hypno-therapy prior to any gene-seed implantation. Occasionally an aspirant will grow too old or prove unsuitable during this process, and those are typically handed over to the Schola Progenium. As required to maintain chapter numbers, the best of the waiting aspirants begin gene-seed implantation. The additional therapy is thought to increase chances of success, and tends to produce a wiser, less reckless scout.
The 10th founding was a transition period for many new Space Marine chapters. The concept of the Emperor's divinity had already gained widespread acceptance throughout both populace and Adeptus Terra, though not yet amongst the Adeptus Astartes. The duality of belief for the Crimson Lions reflects this transitional period.
Like many other venerable chapters, they look at the Emperor as a father, albeit an extraordinarily gifted one. However, they also see him as the living vessel for human divinity, a Divine Avatar to borrow a Thorian term. Though many outside the chapter have difficulty reconciling these two views, with the exception of some members of the Inquisition, they view it as an innate duality in the Emperor's physical and Warp manifestations.