Servator
There be no folly in the Servator. It first comes as a voiceless, formless thing- a wavering in the air as if looking past a flame or across a heated sand, rooftops or stone. It be as a gentle breeze, silent and presenting no danger. It whispers in the mind like a memory of voices. It watches and may make reports. It never sleeps or eats. It unquestioningly obeys the Master. It makes an excellent spy or watcher. Over time it asks for a voice and may learn to mimic and copy the voices it is told to use. It needs to be around the voices it will learn to mimic for several hours. If one says it may have their voice that one is struck dumb and the Servator now has their voice. It may also be that the master, if given "words" or a statement of "you have my voice", may grant that possession over to the Servator. The clever ones may figure this trick. In this it becomes a useful invisible and bodiless messenger. Cunning is used for the next use. The Servator may learn to take on substance first in a misty ghostly form that is easily disrupted by a blow passing through it. Then it may learn the copying of solid forms. It is most useful to have stolen the voice and form of some enemy, obstacles or officials. The form must be given over via sacrifice or agreement given or manufactured by trickery. Sacrifice is the easiest method and that which is given over surrenders it's form and becomes a shapeless mass of flesh. A servant that is the Masters's by oath, slavery or other is also the Master's to give the Servator.
Ayami Noto. scholar. "Lost lore of spirits and occult beings" 2048 T Bronze age kingdom of Epara (Modern eastern Olia)
Summary
The Servator is formless, shapeless and voiceless when summoned. It may learn mimicry and other skills quickly (starting at 1d4 Smarts and other ability and learning skills starting at 1d4, +1 per use until the + value equals the die in use, then it upgrades to the next die type and starts over). Once it has started learning forms it may manipulate material objects as a physical being. It is always watching and learning. If questioned it says it comes from a place without form, voice or material, only thought but without color, sound or shape. It learns these things in the mortal material world but has none of it's own until they are given to it. It presents as guileless and a useful servant.
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The Servator's ultimate goal is replacing Master and will try to be helpful in manipulating things to get there, but it may also elect to transfer itself into the role of any other form and voice it has acquired. Once it has a fixed form it may chose to depart or play as obedient servant until it can make a desirable duplicate and assume that person's life. The Servator is never really under Master's control at any time - the Servator merely plays as if that is so. It needs to be given or granted each thing it acquires in abilities, skills or form/ voice. The one it is taken from loses the corresponding thing in part or whole by the grant. " Let me have our strength here..." The Servator is actually an alien race of formless Rift Mimics and summoning brings a new one. None know their true agenda.
I really like the descriptive imagery for this creature, it paints such a vivid picture in the mind. I also really like the build up of what exactly the creature is capable of.