Brother Filthrot is certainly a fast and nimble Skaven, to be sure; but there are many fast and nimble Skaven. What sets this particular one apart, is that some time ago, he got religion.

Or at least, whatever Warp-inspired madness passes for religion among the rat-people. Brother Filthrot preaches... sort of... mumbling in tongues at times, screaming dire premonitions with foam flecking the corners of his snout at others. His eyes are at times wild with 'divine' inspiration, and at others, cold and dead with prophesies of doom and destruction whispered in a fatalistic monotone.

As far as blood bowl goes, Brother Filthrot views the team as his flock, and his participation in the game as a means to inspire them to greater belief. His team-mates variously regard him as an insane and dangerous influence, with bemused indifference, or (among a few of the more fundamentalist-minded rats) fervent devotion.