Is an Immune creature considered to have the condition without suffering its effects?

Question

In this question asking about a homebrew mechanic involving exhaustion, the accepted answer points out an exploit using a moon druid's combat wildshape - Taking the form of an elemental would avoid the downsides of the mechanic as elementals are immune to exhaustion. The answer then goes on to suggest that the druid would need to have greater restoration cast on her to remove enough levels of exhaution before the wildshape was dropped that the druid does not die outright.

Unless I've missed it, there isn't a specific definition for "immunity" within the rules, so we must read that word with its regular meaning in English. In particular, creatures are listed as being immune to the condition itself, not to the effects of the condition (or "asymptomatic" or a "carrier" of the condition or similar language).

The case in the linked question is even more complicated because exhaustion has multiple levels:

If an already exhausted creature suffers another effect that causes exhaustion, its current level of exhaustion increases by the amount specified in the effect’s description.

As such, my reading is that since the element is immune to the exhausted condition, this clause would never trigger - the elemental cannot be an 'exhausted creature'.

Is this interpretation correct, or is the condition applied but ignored? (And particularly, could elementals gain multiple levels of exhaustion whilst being immune to the condition, for the purposes of ending wildshape for example?)

Answer 1

I disagree with the context given in Urknecht's answer. That answer gives a case of having a condition and then becoming immune to it, but if a character was under the effects of the Heroism spell and someone cast Cause Fear on them, they wouldn't be frightened when Heroism ends. As such, you can't get exhaustion while you are immune to the condition.

However, if you already have exhaustion when you become immune to it, it will suppress the effects of it without removing the condition. This means that if they suffer an effect that causes exhaustion again, the level will still increase, while all effects are being suppressed.

Answer 2

The only thing related to this I could find was from the Sage Advice Compendium. Here is the relevant question and answer (emphasis mine):

If the heroism spell is cast on a character that is already frightened, does it remove the frightened effect?

The heroism spell would suppress a frightening effect that was already on its target. When the spell ends, the target’s immunity goes away and the frightening effect resumes if it has not expired or been removed.

Based on this ruling you would still have the condition but won't suffer its effects.

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For the part about exhaustion:

I couldn't find anything about whether the effects of conditions are still applied if you already have immunity to the condition, but let's consider whether you can still gain a condition if you already have immunity to it.

Under the "Appendix A: Conditions" header in the PHB/basic rules, it states:

If multiple effects impose the same condition on a creature, each instance of the condition has its own duration, but the condition's effects don't get worse. A creature either has a condition or doesn't.

So I would argue that you could get multiple exhaustion conditions and therefore the current level of exhaustion increases, since technically this is just how exhaustion works and it is not the effect of the exhaustion condition. The table in that section shows the effects based on the level of exhaustion, which don't apply since you are immune.

TLDR:

Yes, you can still have the condition without suffering from its effects.

In my opinion, exhaustion level can increase, but you don't suffer from the effects if you are immune.