How does the temp HP from the Conjuration wizard's Durable Summons feature interact with the Find Familiar spell?

Question

The description of the find familiar spell states (emphasis mine):

You gain the service of a familiar, a spirit that takes an animal form you choose. [...]

[...]

As an action, you can temporarily dismiss your familiar. It disappears into a pocket dimension where it awaits your summons. Alternatively, you can dismiss it forever. As an action while it is temporarily dismissed, you can cause it to reappear in any unoccupied space within 30 feet of you.

At 14th level, School of Conjuration wizards get the feature Durable Summons:

Starting at 14th level, any creature that you summon or create with a conjuration spell has 30 temporary hit points.

And the rules for temporary hit points state, in part (emphasis mine):

Unless a feature that grants you temporary hit points has a duration, they last until they're depleted or you finish a long rest.

I'm not quoting the whole thing, but the description is written from the perspective of the creature that has the temp hit points, referring to that creature as "you" and "your".

Say a 14th-level Conjuration wizard casts find familiar. Since it is a conjuration spell, the familiar would get 30 temporary hit points. But how long do these temporary hit points last?

The description for THP says that if the feature that granted the THP has a duration (which it does not), they last until depleted; otherwise, the temporary hit points last until "you" finish a long rest. In this case, "you" is the familiar, and since the familiar is a spirit, it technically should not need a long rest. Therefore, it would last until depleted, correct?

Likewise, the feature says, "any creature that you summon". While the spell states that the familiar, if dismissed, waits in a pocket dimension for "your summons." Would this mean that every time you bring the familiar back from its pocket dimension, it gets a fresh batch of 30 THP? (And yes, I get there is more than one definition of "summon".)

I'm curious how to rule these situations.

Answer 1

The temp HP are generated upon every summoning, and last until depleted or otherwise until the familiar finishes a long rest.

You've quoted all of the relevant rules in the OP. When you receive temporary HP, they last until they are depleted, or otherwise until you have finished a long rest. There's no reason to believe that your familiar doesn't require long rests (they use the stat block of an ordinary animal), so they last until they're depleted or until the familiar finishes a long rest.

They would receive these temporary HP whenever the Find Familiar spell is initially cast to summon them, as well as whenever you use an action to resummon them after temporarily dismissing them (since that's an ability granted by a conjuration spell).

Answer 2

When you cast find familiar, the familiar starts with some temporary HP

Find familiar does "summon or create" a familiar for you, so when the casting is complete, your new familiar should have a nice supply of temporary HP.

But no, the action to call your familiar out of its pocket dimension would not recharge it. That isn't casting a spell to summon a creature; it's just an action you have by the nature of familiars.

The text of the spell does not claim that calling the familiar out of its pocket is summoning. The phrase it uses is "you can cause it to reappear". It merely says the familiar "awaits your summons", as in the standard english meaning of the phrase -- waiting to be called into service.

Remember that the find familiar spell has a duration of "Instantaneous", so even if the spell effect (the familiar) grants you an action you can use later, using that action is not casting a spell, and it's not occurring during the duration of a spell you previously cast. I don't see any way it would count for this purpose.

The Durable Summons feature is about creatures you create or summon with a spell, not about popping your familiar in and out of its extradimensional pet carrier.

The temporary HP last until the familiar rests.

The "you" in the temporary HP rules refers to the creature that has temporary HP. The familiar's temporary HP last until the familiar itself takes a long rest, regardless of what you, the caster, do.