Lantern of Storms. A held slot light item that gives caster bonuses, and
possibly some misc benefits such as vision enhancements for those in room. It
can only be fuled with the rendered fat of powerful monsters that the user has
helped slay, the stronger the monster, the better the stats on the thing,
however the fuel only lasts for a certain amount of time. This would be a
nicer idea if there weren't about half a billion things to do with corpses
already. Maybe an alternate version would be that alchemists could make oils
which grant group combat bonuses or something.