Basically, the pale master is a necromancer that gives parts of their living body up for undead augmentations. For example, the natural AC bonus that the class gets is thier skin turning hard and bony. As they gain levels, they look more and more like the undead that they control. In Tome and Blood actually said that at level 10, most onlookers confuse the Pale Master for an undead.- Palemaster isn't simply mastery of the undead, it is breaking the bounds between life and death, it's in a sense, a loss of vitality, not related to the desire to control and create undeath necromancers have.
- The Palemaster is also striving to serve the existance he previously knew in reshaping his body as he sees fit, to resemble undeath (The undead graft, and the vital changes necessary for the immunities that he gains). Likewise, these changes increase his link to the undeath. Whereas a necromancer would force undeath to do his bidding through spells and the like, a Palemaster differs by being able to use his growing link with the undead to coax them into doing what he wishes. Breaking the boundaries that people usually think exist between undeath and life.
A good aproach I've read might be self-mummification. Here is a caricaturization. (Mind you, this is a subjective view, but an interesting aproach, give it a magical twist, dismiss it, but if it can help to give you a guideline; as long you keep in mind that the Palemaster wishes to defy/shape Death, to twist his own self to ressemble it by "experimenting" on his body)
-First, the pale master makes a cut in the left side of the body and removes all of the internal organs. It is important to be well-rested and nourished before beginning the ritual.
-Second, the liver, lungs, stomach, heart and intestines are washed and packed in salt, which will dry them out.
-Third, the pale master stuffs his empty body with salt and waits for it to dry for at least 12 hours, preferably in a dry area with an abundance of negative energy.
-Fourth, after sufficient time drying, the body is washed with water, then covered with oils to help the skin stay elastic.
-Fifth, the dehydrated internal organs are returned to the body and reconnected with one another. The other organs are discarded. The remainder of the body is stuffed with dry materials such as sawdust, leaves and any linen used during the embalming process.
-Finally, the body is covered again with good-smelling oils.
In essence: taken out, semi-mummified, returned (and also reconnected). Still magically working (Organs) and are required (since the pale master isn't really undead and can breathe, eat, ect).
Keep in mind that not all mummification is done through the old Eygptian techniques. There is also natural mummification, where a corpse becomes dessicated and somewhat preserved. It's conceivable that a Pale master's body could become much drier. Picture the skin becoming leathery and creased, the eyes sinking a bit, the lips drawing back a little to expose the teeth more. Finger and toe nails would appear longer as the skin retracts, cheeks would appear a little sunken. Losing all that moisture, they'd be much leaner looking, and might actually fit the phrase, "Death warmed over."
About the dead and controlling the dead:
Animate/Create spells make a dead body into an undead creature. At some point in casting this spell, a corpse becomes undead. Whether that happens at a distant and it's summoned to you, or whether you're carrying part or all of the corpse to be animated on you is up to you.
Summon Undead abilities are summon abilities. This represents a pale master's connection with undeath, and allows him to call his undead buddies to his aid. Like summon creature spells, they don't make the creature, just call it to your location and bind it to your will.
Sources: Libris Mortis, Tome of Blood.
- - -
I'd suggest the Pale's master summon to reflect a 'mummy' creation that the pale master is constantly building and improving ( as implied by levels) based in part of his own organs.