Something I made when Zachareth was announced to be a traitor for Rune Wars. Comments, improvements, balance suggestions are all welcome.

Fun idea but Zachareth should be a more "dark" hero since he is a bit like Belthir with an hybrid loyalty sometimes for good si de sometimes bad.

So a strong ability and feat but with hard side effect

There should be a cost with the ability (either for the Baron himself or the recipient). I love the idea, but it can get stupid-powerful. Simple trade off is all it needs.

Heroic Feat = Again, love the core idea. There's just fiddly mechanics about "how much health, when does he take over, etc" that need to get ironed out (the un-fun part of design)

The hero ability is way too strong, even with a trade off.

Zachareth the Runemaster exhausting his own Ghost Armor or an Apothecary's Brew Elixir to refresh Bottled Courage will essentially grant a free additional attack every round.

That's stronger than any other hero's heroic ability. And that's just one example. Bushwhack would be similarly powerful. It could also be used to grant additional surges from Mastery skills, or additional healing, so its super flexible too.

Definitely need a cost on the ability: "suffer 1 ft to refresh..." or "during your turn exhaust one of your skills to refresh..."

The Feat is a good idea, but there is some missing verbiage. I have a custom class skill that has this sort of mechanism and had to flush it out this way (use any of this verbiage you like):

"Place your hero token under its base to identify this monster" and, "The monster recovers half of its life total, rounded down" and, "The monster activates as a familiar and is treated as a hero figure" and (If you want to be able to use monster abilities), "You control all decisions and actions of this monster. All monster abilities referencing “hero” are replaced with “monster” and vice versa." This all becomes very instructive and falls victim to space-limitations on the hero sheet.

Also, I don't think you considered the implications of the ability/stat trade-offs. You may need him to roll a brown defense die and reduce his health to 10 (or 8 health and keep the gray die?) or reduce his Speed/Stamina equation given the powerful ability.