On another question – Is an Immune creature considered to have the condition without suffering its effects? – it was concluded that a creature could gain exhaustion levels, while being immune to the effects of those levels.
Assume we have a druid/barbarian (Berserker subclass).
The druid hasn't been sleeping for a few nights, and so has 2 levels of exhaustion. There's a blizzard going on, bestowing another level of exhaustion.
He goes into a frenzied rage, taking the exhaustion level to 4.
He goes into the Wild Shape of an elemental, gaining immunity the effects of exhaustion. He then sprints enough times to the point where each Dash increases the exhaustion level by 1.
The rules aren't exactly clear whether exhaustion immunity prevents the exhaustion level from increasing, but regardless, he won't suffer the effects of exhaustion.
If he dashes enough to increase the exhaustion level to 6, what happens if he gains another level of exhaustion? Is it possible for exhaustion level to increase past 6?
If so, would this increase the amount of healing/spells/potions that remove exhaustion levels needed to decrease the exhaustion level to a point the Druid could drop Wild Shape without dying?
Best Answer
While in the form of an elemental, the druid is exempt from exhaustion.
Elementals do not suffer from exhaustion effects
The vernacular definition lists exempt as a meaning which is apt for this application of it, and the immunity rules don't more specifically define the term. Immunity to fire means one does not suffer burns. Immunity to exhaustion means one does not tire.
Elementals do not accrue exhaustion.
Similar to being immune to a damage type. It doesn't mean that damage is taken and ignored, it means that the immune creature takes no damage of that type. Similarly, when something would add a point of exhaustion to an elemental, it does not. So in this case, the druid is not accruing exhaustion while they're an elemental.
Specific to your example, in elemental form the druid can sprint as often as they like without ever increasing exhaustion.
When the druid reverts back from an elemental, they're still at the same exhaustion level as when they changed form.
The text of wild shape ability is mum on removing effects, so it doesn't explicitly do so. There exists a consensus about changing form supressing effects that do not apply to the new form. Changing form, such as with polymorph, can suppress effects but doesn't cure them. Shows up again here.
It is not possible to get to an exhaustion level above 6.
By taking an form immune to exhaustion, they cannot accrue exhaustion. If taking a form that is susceptible to exhaustion, and they gain more levels of exhaustion, the effect is death. This causes the druid to revert to their original form. Since death does not remove exhaustion levels (despite it being the longest rest) the druid still has 6 levels of exhaustion which has the effect of death.
In short, if immune to exhaustion, a character can't get to 6 levels of exhaustion. If not immune to exhaustion, a character suffers the effect of death upon getting 6 levels of exhaustion.