Tallpox

When summoning Daemons, it's easy to make mistakes.  When Wex the Pustulent first attempted to summon a Plaguebearer of Nurgle, his faith shook for momentarily.  He stumbled over the words of the incantation and, when he finished, a mangled and broken mound of flesh and bones lay on the ground before him.

Not ready to accept failure, Wex and his followers gathered pieces of cloth and metal and attempted to mend the broken thing that lay before them.  Each bestowed upon it their gifts from Grandfather Nurgle, strengthening its crippled body.  They stitched its flesh together carefully, and bound its long, frail legs with cloth bandages.  One leg was so deformed, it had to be screwed into a rusted metal splint.  After weeks of diseased writhing and pitiful mewling, Tallpox was finally able to stand on its wobbly legs.  Only then did they realize that the daemon, though weakened, towered over mortal men.

Years have passed since first it was summoned and Tallpox has grown stronger.  Though it still needs its legs splinted and bound to walk, Tallpox has grown into a formidable combatant and an invaluable member of the warband.