Two sisters.

I don't think the dwarven GENERALS would agree to sell their homeland for an artifact. Secondly, as can be seen from the dialogues, they still believe in their victory, that the capital is impregnable, and that the quartet of leaders is invincible. Furthermore, hiring a dwarf with so many cities – and a highly upgraded dwarf at that – is an overpowered advantage on this map, which immediately makes the player invincible.