KYUBEY is an Incubator, a member of an alien civilization with the ability to grant adolescent girls a wish in exchange for transforming them into Puella Magi and tasking them to hunt Witches. Incubators do not appear to state outright falsehoods, but are known to commonly give partial information in such a way that all but the most cunning of their clients do not think to ask about potentially-crushing details. They also allegedly lack 'emotions', though what this means is not particularly clear given a clear ability to prioritize information. A near-total lack of sympathy is apparently part of this.
Kyubey is the only Incubator encountered in the Quest thus far by AKEMI HOMURA.