If mana recovered slowly enough, and mages could pass it on freely between them, the ephemeral force would become a valuable trading commodity on its own.
What if a mage passes his powers on to his firstborn son, and a female mage to her first daughter, leaving the parent POWERLESS? A plain mortal, a sorcerer no longer, all wizardly might gone?
Or: what if a female wizard recieves the power of a mage who sires a child with her? Could lead to promiscuous witches and overly careful mages.
What if cancer is not an ailment if one has a will powerful enough, and knows what do do. What if one using the right techniques could control it and use it to become immortal, or to grow into something else?
Pick up a pathology/microbiology book, and add the diseases/syndroms to your game. Your players will freak out.
Coughed at? Diphteria. or tuberculosis?
Drunk from a muddy stream? Or just walked through? Well, let us introduce you to schistosomiasis...
Hit by a stream of energy? Too moch mana is ust like too much radioactivity - perhaps all mages could develop cancer early if too powerful...
The Jiangsi was the name of an undead being in Chinese folklore and mythology. Usually translated as zombie or vampire for Western palates, the Jiangsi was really neither. They appeared as simply risen, fresh corpses. They moved (peculiarly!) by hopping rather than walking, and sought out the living to suck the Qilife force from their victims.
Perhaps significantly more interesting than the Jiangsi itself, was the lore surrounding them. "Zombie wranglers", or "Corpse Herders", usually Daoist priests, were men tasked with delivering these undead beings back to their respective home towns. Tradition in China placed great importance and emphasis on the return of the dead to their homes and families, and thus the corpse herders came to be. By using magick words and talismans they would animate the dead, and by placing specially inscribed parchments of paper over the Jiangsi heads and faces, the corpse herders would be able to control the hopping corpses. Then like pied pipers, they would lead processions of subdued undead, across many miles, rhythmically chanting and ringing tiny bells.
Special inns were built across China to house these undead caravans, as the zombies could only travel by evening and night, the sun anathema to them. Rows of doors opening to barely a closet-space, lined the walls of these special establishments. Behind these doors, the corpses would be stored upright while the corpse herders rested in rooms.
The Jiangsi under the control of a corpse herder were quite harmless, merely hopping after him, silently and without complaint, for weeks and months. If however, the magicked parchment would somehow be removed from their faces, the creatures would immediately seek living humans to kill. Their thirst for Qi was unquenchable.
The job of a corpse herder was an interesting one to say the least.