Fester is a clan clinging to a distant glorious past, having once held a seat on the council of Thirteen at the time of the Black Death. To their dismay, the last millennium has provided nothing but ample misfortune and a steady decline, but compared to recent events, most of their historical setbacks pale in comparison.
The breeders of Clan Fester have recently somehow contracted a mysterious disease dubbed 'the Brood Blight' causing infertility among their breeders. The loss of breeders would be a deadly blow to the manpower, influence and strength of any Clan, but to make matters worse, the contagion alienated Clan Fester from their superiors: Clan Pestilens.
When not even the plague merchants of Pestilens could remedy Fester's affliction, the weakened clan was cut off like and infected limb as soon as the Pestilens Deacons had learned as much as they could about the disease.
Clan Fester was left to either slowly decline into extinction, or to be sacrificed in suicidal offensives in an attempt to spread their disease to the enemies of Clan Pestilens. Either option spelled nothing but doom for the stricken clan.
In these desperate times entered Grey Seer Rasknitt, who with willy trickery and devious scheming gained influence over the Warlord of Clan Fester, having persuaded him that only Rasknitt has the cure for the malady affecting them
'Move north, to the lands of the man-things, and take Ubersreik-den, and the magnificent Rasknitt shall deliver Clan Fester from their misery.'
- Warhammer: End Times - Vermintide.