The PCs paid for two weeks worth of sage research (two skill 14 Research rolls) into the culture, history, and any interesting tibits on the Osirians, whose pictographs cover the giant orichalcum doors on the "Gate level" (formerly "the apartment level") of Felltower.
The Osirians were an ancient people who lived in a desert land. Reports variously place them in a desert south of Stericksburg, a river delta south and east of Stericksburg, or on another world with colonial pockets in various places throughout the world. They were eventually destroyed by undead-hating neighbors in one of the great anti-undead crusades by the Inquistors of the Holy Flame.
The Orisians worshipped, or respected, or admired, death. Life was considered a transitory state before the eternal existance after death. As such, the most important thing to do was prepare for the afterlife with all attention and effort. They originated the creation of mummies. Such mummies have their vitals removed and are thus protected from harm. They are usually vulnerable to flame, however.
They worshipped a wide variety of animal-headed gods - each representing a handful of godly tasks. A bird-headed god of wisdom, a hyena-headed god of undead, a cat-headed god of marriage; the home; and protection, a snake-headed god of magic, a falcon-headed god of war, and a faceless god of evil. Their main symbols include a hoop-topped cross called an ankh (a symbol of eternal unlife), a crooked staff, and a flesh-eating beetle. Many half-man half-animal beasts populate their mythology and imagery. These include lion-men, scorpion-men, snake-men (usually snake-headed men), and crocodile-men. It's assumed these beings once existed as godly emissaries or just perfectly natural animal-man hydrids.
The Osisians had a very strict class system - priests, soldiers, merchants (including engineers), farmers, slaves. Class was established at birth, changeable only by the gods, and delinated your role in society. Their rulers were high priests selected by their gods. The better one's class the better one's afterlife, which was to be enjoyed in a world of blackness and eternal death.
Osirians were especially fond of mathematics, puzzles, an astrology. They are famous for word puzzles, word play, math puzzles, and traps - often all at once. They felt that death was the ultimate reward, but that killing their enemies before they could properly prepare for death (and thus assure a pleasant eternity) was the ultimate revenge. Enemies slain would be granted to the slayer - be it a warrior, priest, or trap-designer - as eternal slaves.
They were greatly impressed by knowledge, wisdom, and "proper" undead - those prepared and consecrated to their gods - mummies, skeletons, and liches. They despise those undead who prey on the living - such as vampires or wights, and those who come to unlife from anger and not godly blessing - such as draugr and spectres. Zombies were considered unclean. Ghostly beings - ghosts, phantoms, shadows - are considered the damned, as they lack a proper undead body. Mummies, correctly prepared in the traditional way, are the ultimate undead and therefore the best way to spend an eternity.