The boss of Tower Knight Archstone.
Knight-like demon, the Penetrator wields a long Penetrating Sword that glows light blue during every blow. An 8-foot tall, agile knight wearing what appears to be a fusion of European and Asian-style armor. It wields a sword which is thin and longer than most lances. Its greaves are very similar to the Gloom Leggings.
Penetrator is the corrupted form of Metas, the knight of the lance, a knight of the round table in Boletaria. Before the scourge, he wielded a straight sword which was longer than most spears and could kill a man with a single thrust. He wields a Demon Soul powered form of the penetrating sword which has been used "to cut down many warriors who attempted to slay the Demon." Penetrator seems to have a hatred of both the fat ministers (as he kills one when entering the boss chamber) and Biorr (as he mostly attacks Biorr and ignores the player).
Penetrator's Silver demon soul can be crafted into two different weapon buffing spells. Light weapon draws from the power inherent in the sword and cursed weapon draws power from violent acts committed with the sword.
Metas appears later in the level as a black phantom wearing a mixture of fluted chest armor and plate armor for his arms and legs. He wields his penetrating sword in battle. Fluted armor is worn by knights of the Southern kingdom of Latria, but Metas mixes it with armor common to Boletarian soldiers. The fluted armor would seem to indicate Metas is not native to the Northern kingdom of Boletaria, but is actually from Latria. Another possibility is the chest piece of fluted armor belonged to his father and his father was Latrian, but Metas is in service to King Allant. Another possibility is Metas is the son of Lord Rydell (who is suspected to be the little brother of King Allant) then that would make Metas nephew to King Allant and cousin to Ostrava. This blood relation would explain why a Latrian would serve the Northern kingdom and also how the Northern and Southern kingdom co-existed peacefully with each other.
The corpse of Metas, carrying his penetrating sword, can be found on the overhang above the gate the fat Minister closes near the rolling, flaming boulders in the Inner Ward.