This weapon can only be obtained by killing the Mallorn Ent boss, or getting it from creative mode. When slain, this boss has a 50/50 chance of dropping the mace. Because you must have a negative Fangorn alignment to summon and slay the Mallorn Ent boss, it's impossible for most good players to obtain this weapon without killing another player or having them give one to you. The weapon is therefore difficult to obtain.
As of Public Beta 33, it requires Mallorn planks to repair and reforge, despite being a weapon for evil players.