There is nothing noble in the Skavenbrew, and the ratmen who concoct it would be baffled by the very notion. It is a foul distillation of raw warpstone, ground bone, and secret ingredients no sane creature would name, cooked in the reeking vats of the under-empire and doled out to slave-soldiers on the eve of battle. Those who choke it down are seized within moments by a frothing, screaming frenzy, all fear and pain burned away by the poison flooding their veins.
The Skaven prize the brew precisely because it is so cheap in the only currency they respect — the lives of their own. A slaverat too craven to charge becomes, with a mouthful of Skavenbrew, a shrieking berserker that flings itself at the foe heedless of wounds. That the elixir also eats the drinker from within, boiling the blood and rotting the flesh, troubles the warlock-engineers not at all; a warrior who dies an hour after victory has served his purpose.
Even among the ratmen the brew is handled with a certain wary respect, for the vats have been known to slop over or ignite, and a careless warlock may find his whole warren transformed into a heap of twitching, foaming corpses. The Skavenbrew is not a treasure to be cherished but a weapon to be spent, as the Skaven spend all things: recklessly, wastefully, and always at someone else's cost.