Skeletal Champions and their cousins Skeletal Magi are powerful undead creatures who retain their sentience after being animated as undead, as well as their class features. This alone makes them terribly strong undead creatures that are created rarely by powerful necromancers.
Few create skeletal champions or magi because they are not innately under the control of the creature who animates them, and thus few use such magics on their fallen enemies unless they can somehow compel them after they have revived them as undead. For this reason, the act of creating a skeletal champion or skeletal mage is something few necromancers undertake lightly, and usually only do so for their trusted allies.
Creating an a Skeletal Champion: Creating a skeletal champion or mage is a relatively straitforward process, but the creation of the undead is more complicated than merely casting animate dead and being done with it. It generally takes a ritual that requires at least ten minutes. If the ritual is interrupted it must begin again from the start. During the ritual the caster must set up a ritual circle with some candles. The exact number of candles is irrelevant, but most use as many as is aesthetically pleasing to the caster (usually 3, 5, or 7 arranged in a diagram). During the ritual, the caster must cast animate dead on the corpse and transfer a portion of her own essence into the undead as she is animating it. This act generally is preformed by a symbolic gesture that represents the passage of the casters soul energy to the corpse to be animated. Upon completing the ritual, the spellcaster suffers 1d4 points of Intelligence, Wisdom, and Charisma drain from the transfer of energy to the newly created undead. At this point, the undead creature animates as a Skeletal Champion or Skeletal Mage as chosen during the time of the ritual (skeletal magi must have possessed at least one level in a spellcasting class, or else they become skeletal champions by default). The caster may, optionally, expend 5,000 gp worth of gemstones as part of the ritual to avoid suffering ability drain. These gemstones are consumed in the process when the ritual is complete.