In addition to their normally chosen spells, some Wizards know the following spell:
Howling with an obscene pleasure, the Grey Seer trembles while jumping back and forth, summoning a pestilent darkness which soon starts to spin around them. The Seer points towards their foe as dark shadows surround them. With a sickening lurch the fabric of reality is torn by the twisting power of the Great Horned One. Under the cloak of shadows it can be seen how their victim's shape contorts, transforming into shrunken rat figures.
Curse of the Horned Rat is a direct damage spell with a range of 24" that can target Infantry units. The unit suffers 3D6 Hits, though no single model can be Hit more than once. Each model Hit is automatically slain with only Magic Resistance being allowed as saves against the twisting power of the Horned Rat. If the whole unit is removed as casualties, replace them with a number of Clanrats equal to the number of casualties, with any normally allowed equipment or command, facing the same direction as before. The casting player now controls this unit. If the casting player does not have enough models to replace the entire unit, transfigure what you can, the rest are considered destroyed. If the number rolled is not great enough to replace the whole targeted unit, then remove as many casualties as the number rolled – they simply mutate and die, or were slain by horrified comrades.