I can't make sense of Raythen's Hero Ability. Am I just overthinking it? It reads:

Once per turn, you may suffer 1 [fatigue] to allow 1 hero on the same map tile as you to reroll an attribute test. He may use your attribute value instead for the reroll.

What is meant by "once per turn" in this context?

1. Once per Raythen's turn? (This would really only benefit him, wouldn't it?)
2. Once per every player's turn? (Better, and balanced by a restriction on how many times the same hero can reroll.)
3. Once per round? (Least likely based on RAW, but possibly what was intended.)

I thought I'd check here to see if I'm missing the obvious before asking FFG.

Once per any hero's turn and the Overlord turn. Basically he can do it anytime, but only once per turn. This is to prevent him being able to spam it. For example, the Overlord plays the Befuddle OL card, the hero fails, so Raythen can trigger his ability. The hero fails again and this time Raythen can't trigger the ability.

Okay, so #2. That's how it's written, but I'm not used to seeing "once per turn" used this way, so I wasn't sure. Thanks!

You will also see it used in Elder Mok's ability.

The important thing to keep in mind is that, as Omnislash noted, the OL is also a player and thus has a turn.

So, once, on the OL's turn, and once on every other hero's turn, Raythen (and Elder Mok) can use his heroic ability.