Swampmist

We actually have seen the Moulder allegiance ability, or atleast one of them: At the start of the first battle round, before determining which player has the first turn, For each Master Moulder in your army, choose a Clans Moulder Fighting Beast (same beast can;t be chosen more than once). Those beasts gain d3 wounds (roll seperate for each one) and can reroll failed hit rolls of 1 with melee weapons.