The Malleus Argyrum is the personal weapon of Grand Master Aldrik Voldus of the Grey Knights' 3rd Brotherhood.
Crafted over a standard century by the blind smith Hulliver, this beautifully weighted Force Hammer is a conduit for its user's psychic energies.
So empowered, it streaks through the air as though it weighed nothing at all, only to strike with the force of a caged thunderbolt.
- Gathering Storm - Part Three - Rise of the Primarch (7th Edition), pg. 124