Is a mount considered an "ally" for the purpose of Pack Tactics?

Question

I suppose this applies both to NPCs and player characters.

Specifically, someone proposed the idea of a PC kobold (a playable race from Volo's Guide to Monsters, p. 119) as a paladin, summoning a mount, and attacking with constant advantage as a result. This made me wonder: would that actually work?

Kobolds' Pack Tactics feature has the following description:

You have advantage on an attack roll against a creature if at least one of your allies is within 5 feet of the creature and the ally isn’t incapacitated.

(The monster statblock and its variants have an identical trait, except that it is written in third person.)

Would a mount count as an ally for the purpose of Pack Tactics?

Answer 1

Yes, as long as the mount is within 5 feet

An ally is not clearly defined in 5e, so we can use the English definition:

a person, group, or nation that is associated with another or others for some common cause or purpose

Ally in the case of D&D 5e is almost certainly meant to include animals since wolves get the Pack Tactics trait too so we just have to assume the mount has "a common cause or purpose"

Find Steed

[...]

Your steed serves you as a mount, both in combat and out, and you have an instinctive bond with it that allows you to fight as a seamless unit.

(emphasis mine) fighting as a seamless unit certainly implies a common cause, so a found steed would have this qualification as an Ally.

Most steeds has some level of intelligence (comparable to a wolf) so it can share other goals with you too, but a found steed can have more advanced goals (see this question on creature sentience).

Even a normal steed should count as an ally, but a found steed has extra qualifications as an ally.

Is the mount within 5 feet?

There are some cases where your mount won't be within 5 feet of the enemy (such as if you are attacking a creature 5 feet above you and you are at the highest point on your mount), but typical mounted combat will place your mount within 5 feet of any creature you target in melee.

Additionally, attacking with a reach or ranged weapon would not necessarily qualify as the ally needs to be within 5 feet of the creature you are attacking, just make sure you keep that aspect in mind.

Answer 2

Yes, the mount would count as an ally provided it would assist you in combat.

Would it assist you in combat? A found (discovered; such as in the wild) or purchased mount doesn't automatically fight when you do, though they can certainly be trained for combat.

In the example of a paladin's mount (which is not a found or purchased mount), however, it is combat trained to serve as a mount in combat. Due to its increased intelligence and telepathic bond, I would rule it to be threatening squares even if you were not mounted.