Gandalf

[Amarinth]

yes, gandalf was sent back by illuvatar himself, as voronwe quotes. i'm going on a stretch here and hypothesize that only illuvatar anyway could have summoned gandalf/olorin from "wandering in the dark", the unprecedented(?) death of a maia incarnate.

by the same token, halfir does have a point in stating that gandalf needed to undergo some "transformation" or the archetypal "rite of passage". the five maia having been shorn of a greater part of their power when invested as the istari have transformed to some finite form of incarnation, and expectedly with only a reincarnation of olorin "retaining" greater power and stature would he be able to supersede and subsequently overthrow curunir.