The mage can alter the form of an ectoplasmic manifestation[1][2], shaping it with his will into whatever form he desires. He must contend with the will of the mage who conjured the ectoplasm or the ghost who manifests through it.
Successes are used as Potency to wrest control of the ectoplasm from the mage or ghost who currently controls it.
Mysterium Rote: The Seal of Harafax
Named after the mage who first formulized it, the title of this rote also refers to the image of ectoplasm as hot wax, to which the mage’s will is applied like a signet.