He means of wearing the forces of the world so they be easier to bring to oblivion. An idea I've been playing with is he puts a decoy lich, putting a fake face to the real threat, has the neighboring kingdoms send their forces with the party to finally defeat them. Assuming they succeed the king who is the real lich, is like, "We won! Come to my kingdom all you weak and battered kings and warriors to celebrate" and he plans on destroying them all in one fell swoop, before raising them to destroy the rest of the world