The Heralds of Galactus were individuals who were imbued with a fraction of the power cosmic by Galactus himself. Some well known heralds include the Silver Surfer (Norrin Radd of Zenn-La), Terrax the Tamer, Nova (Frankie Raye) and many others (listed here).
In the animated series Avengers Assemble Season 2 Episode 25: New Frontiers, Iron Man briefly served as the herald before leading Galactus to a trap (I won't reveal details about the episode's plot). This got me thinking.
Was there, at any point in time (in the comics), an Avenger who was turned into a herald (voluntarily or otherwise)?