If "Gandalf the Grey keeper of Narya" is the guide of the fellowship, and the fellowship is in Rivendell on the first turn of the game; can Gandalf use "Narya the Great" ability to activate the elves and move them directly to "At War"? Or does Gandalf have to first be removed from the fellowship to use the ring?
He must be separated from the Fellowship in order to use that ability. From page 39 of the base game Rulebook:
While a Companion remains in the Fellowship, he may not have any influence on the game except for his “Guide” ability (if he is the Guide) and for his influence on the Hunt for the Ring (see pages 40-43).
"War is much more fun when you're winning!" - General Martok