How do you handle shapeshifters with accumulated fatigue levels turning back into humans? HoH:MC explains how to handle wounds, but is quiet on the topic of fatigue levels.
A magus turns into a bear, expends four fatigue levels, which – given the bear's extra fatigue levels – puts him at Weary (-1), and then reverts back into human form. Is he Weary (-1) or Dazed (-5)? The latter would obviously result in a lot of "overfatigued" shapeshifters falling unconscious for longer periods of time upon reverting form – I'm just curious if that's intended. Obviously, it would work the same the other way around, i.e. a fatigued shapeshifter turning into an animal form with extra fatigue levels.
I'm not sure it's canon anywhere, but I'd go pro-rata. If a bear had 10 fatigue levels, and a human 5, then if the bear has 4 fatigue after shifting, the human has 2 levels of fatigue. A human with 2 becomes a bear, it's 4.
The question is what to do if the pro-rata doesn't give an absolute number. Round up, down, roll a dice?
My own house rules is that:
a) You always end up at the same tier (Weary, Tired, Dazed, etc) as you were in. This is the most important part.
b) When the shape you change into has multiple fatigue levels at the same tier, you won't end up with more levels than you had in your old shape. This is so you can't recover fatigue level just by changing shape back and forth.
Example:
A bear has fatigue levels (RoP:M p141): OK, 0/0, -1/-1, -3, -5, Unconscious
A human has fatigue levels: OK, 0, -1, -3, -5, Unconscious
So, assume a human has lost two fatigue levels and is down to Weary (-1)
They change into a bear, and will still be at Weary (-1) but now with a total of 4 lost fatigue levels. Losing one more would take them to Tired (-3)
Change back to human, and they will still be at Weary (-1).
One reasonable variant is that you always end up at top of the tier of the new shape, so in the example above the human changing to a bear would end up Weary (-1) with 3 lost levels. Losing one more and they would still be at Weary.
In that case if they were at 4 lost levels in bear shape, changed to human and back to bear shape, they would recover 1 fatigue level in the process.
A matter of taste as to which variant is preferrable.
The only rule I know of about switching between different sets of Fatigue isn't for this, but for swapping between two people. That would be in ArM5 p.134 under Gift of Vigor. That spell has you swap with another person. In that case you end up at the same Fatigue level (Tired, Weary, etc.) regardless of how many spots the other had at lesser Fatigue levels. So two bear Bjornaer could not just use this back and forth to remove all their Fatigue. Now, it doesn't specify what happens to the current level if there are multiple spots for it. Personally, I would mark them all off to avoid abuse.
That does suggest Lee's and ErikT's approaches are appropriate.
Now, this doesn't stop abuse such as all magi turning into boars to cast their spells and then transforming back. This is particularly noteworthy with things like Life-Linked Spontaneous Magic, Life Boost, and Imbued with the Spirit of (Form). And it does allow a bear Bjornaer to recover faster by using Fatigue levels as a bear and becoming a human to rest. But it solves several problems and is easy to implement.
I think I've reached a ruling that seems fair to me. Presented here for judgment:
A shapeshifter shifting back from animal form is at the equivalent fatigue level in human form (i.e. Weary = Weary, regardless of how many Weary levels the animal form had). Shifting between human and animal form maintains partial fatigue levels in animal form. An animal recovers all fatigue of a given level at once (e.g. all Weary levels dissipate after 10 minutes of rest).
This is a small buff to fatigue recovery for animals, but avoids any shenanigans of switching to a more favorable form for fatigue recovery (be that human or animal, depending on ruling).
Sounds reasonable. There just is no perfect solution; reasonable is the best you can hope for.
Just for awareness, this still doesn't prevent shenanigans for Fatigue recovery. Consider this case: I have Life Boost and want to throw 4 Fatigue into my spell. As a human I would drop to Dazed and need 1 hour 42 minutes to fully recover. But if I transform into a boar to cast the spell, I drop to Weary; now I can recover or transform back and recover in 12 minutes.
... or – under your ruling – you'd transform into a boar to cast and back into a human to recover the fatigue in the same amount of time as in your example. So there's really no difference there.
I honestly don't see the problem. If someone switches to cast a spell, and has done the work to be able to cast in an animal shape, good luck to them.
If a magi need to fatigue spont, they cast the spell and then wait 2 minutes. Fatigue level back, rinse and repeat. If it's time critical, changing to an animal takes time, so it has it's own cost.