If you prick me... my power grows inestimably...
Witches in a puddle of blood with the "elemental caster" style trait receive a -1 to action points for every spell they cast.
I'm recommending witches be able to cast a spell (probably at lvl 10) called "Blood Rain". Blood rain's primary purpose would be to cover everything in blood... but as a side effect is a small chance to infect enemies with "Disease".