Does the Animal Companion from the Beastmaster Ranger subclass get additional Hit Dice as the ranger gains levels?

Question

We're using the Dungeons and Dragons 5th edition players handbook only. The Ranger's Companion section (PHB p. 93) seems, for the most part, to be pretty clear. The part about hit points states:

It's hit point maximum equals the hit point number in its stat block or four times your ranger level, whichever is higher. Like any other creature, it can spend Hit Dice during a short rest to regain hit points.

Since the PHB doesn't specifically say otherwise I assumed that you take the Hit Dice from the stat block along with everything else. This means a lvl 6 Ranger's companion has 24 hit poins but only 2d8 hit dice. As the Ranger gains levels the companion's Hit Dice become progressively less impactful. At lvl 20, when the companion has 80 hp, they have become almost meaningless. Since the class lacks any feature for having your companion regain HP (apart from wasting your precious spell slots in it) I wonder if this is intentional. Or was the intention to have the Ranger use the faithful companion they might have had for years as expendable cannon fodder?

To me this seems like yet another disappointing feature of an already underperforming subclass of a generally underwhelming class. Every player class gains Hit Dice as they gain levels so shouldn't it be the same for animal companions?

Answer 1

The companion does not gain any more hit dice as the ranger levels up.

The number of hit dice of the companion is fixed: the statistics that are different from the basic stat block of the beast are enlisted in the ranger feature description. Hence, if the DM allows to pick a Dimetrodon as a companion, they will have 3 Hit Dice to spend, regardless the ranger's levels and the HPs they have.

If the number of hit dice would have been increased as the ranger gain level, the feature would have pointed it out.

For comparison, see the Drake Companion from the Drakewarden subclass:

Hit Points 5 + five times your ranger level (the drake has a number of Hit Dice [d10s] equal to your ranger level)

The Beast companion is not gaining levels.

You wrote

Every player class gains Hit Dice as they gain levels so shouldn't it be the same for animal companions?

Since the beast companion is not gaining levels, they are not gaining any more hit dice. If the DM decides to modify the subclass such that the companion can have a class and therefore they can level up, then normal progression applies.

There are other ways to restore HPs.

You wrote

Since the class lacks any feature for having your companion regain HP (apart from wasting your precious spell slots in it) [...]

Actually, there are several ways to make the companion restore hit points, you do not need special class features: Cure Wounds from other characters and/or temple, potions of healing and do not forget long rests.

The companion is a "normal" creature (of type beast), not a magical one: they are a creature that can be healed following the common rules.