Call the Hunt, the 14th-level Path of the Beast barbarian feature, says:
When you enter your rage, you can choose a number of other willing creatures you can see within 30 feet of you equal to your Constitution modifier (minimum of one creature). You gain 5 temporary hit points for each creature that accepts this feature.
This seems to suggest that any creature seen within range is eligible to accept the feature and thus grant you temporary HP. From most obvious to most absurd, this might be:
- your ally
- your ally's familiar
- an NPC bystander
- a passing squirrel, dragonfly, bird, or other animal
However, in addition to providing a benefit to the barbarian, this feature also provides a benefit to the willing creature:
Until the rage ends, the chosen creatures can each use the following benefit once on each of their turns: when the creature hits a target with an attack roll and deals damage to it, the creature can roll a d6 and gain a bonus to the damage equal to the number rolled.
Clearly, this benefit is only relevant for a creature who is able to make an attack and desires to do so.
Therefore, I wonder: Is a creature only eligible to accept this feature if they're able to benefit from it directly? That is, do they need to be able to make an attack (unlike many familiars) and do they need to have an enemy present that they're ready to attack (unlike most bystanders and random fauna)?