Too bad that is has to be non-neutral. There goes my idea of using Ally Radagast and finally making him broken. Oh well, Messenger of the King is still a great card in other respects. I guess. grumbles
[Update] Having gone through all unique neutral allies in the game, I genuinly wonder why this restriction was put in place. Allies like Core Gandalf, Saruman and Wilyador would leave play at the end of the round, so that wouldn't be viable anyway. Thalion has build-in Heroic-ness. That leaves Treebeard and Radagast, who both have innate resource generation. However, they may only use those resources for specific ends and are not assigned to any of the usual spheres. Surely that must off-set the advantage of having them produce an extra resource if they were a hero. Am I missing something here?