How many hit points does the Beast Conclave ranger's animal companion have?

Question

I like the Revised Ranger UA, especially the beast conclave, but don't understand how the animal's hit points are determined.

For example, a wolf is listed as having 11 hit points (2D8+2). So at 3rd level, would a wolf companion have 11 hit points, or would it work like a 1st level PC and have 18 hit points (max number on initial hit dice). I'm also confused because a wolf has +1 constitution, I don't get from where the +2 comes.

As you level up, do you add 2D8 or 1D8 hit points to the companion's HP total?

Assuming you didn't increase the wolf companion's constitution at level 4, what would the hit point total be? 11 (original HP) + 1D8 + 1 (con modifier) or something else?

Answer 1

Aside from the specific changes that the Animal Companion feature makes to the wolf, it retains its statistics from the Monster Manual, so it begins with 11 hit points.

Per the class feature as described in Unearthed Arcana: The Ranger, Revised:

For each level you gain after 3rd, your animal companion gains an additional hit die and increases its hit points accordingly.

This works like any hit die. The wolf's hit die is a d8. When you level up beyond 3rd level, roll 1d8 + 1 (CON) and add it to the wolf's current hit point total to determine the new hit point total, bringing it to (3d8 + 3).

Alternatively, take the average value. Per DMG p. 276, the average for a Medium size creature is 4.5 HP per die on a d8. The wolf's new HP value is 17 (3d8 + 3).

If you increase the wolf's Constitution score when you receive an Ability Score Improvement, be sure that you update the wolf's HP total to account for the new modifier.

The formula for HP is: $$n\text{d}X + (n \times\text{CON})$$

where \$n\$ is number of hit dice and \$X\$ is the hit die value.

I have included both the option to roll for the new hit die or use the monster average because it is up to your DM to decide the method. Traditionally, taking the average is the approach used for NPCs and monsters, including animal companions.