meredith's restriction is now gone, he said so himself this chapter which is why he was able to change, so his powers should be back which means he still has the original source of mana and not affected from his restrictions anymore. therefore his power should still indirectly affect the magicians mana. because meredith/mikel said that the empire's source of mana is directly from the giant/ meredith, as meredith= giant. but thats only if the theory of meredith=giant is correct.