Eidolon HP Calculations (and Synthesist)

[Veldan Rath]

How are these calculated?

D10's + Con, yes, but if you use static rolls, is it 8 + Con?

[Tar-Tar]

It's 5.5/hit di. So it gains 5 + Con for its first hit di, 6 + Con for its second, and so on. It's the same for animal companions and monsters.

[Veldan Rath]

Yeck...oh well.

[joeyfixit]

Huh? Why wouldn't it be 10+Con for the first hit die, 6+Con for every subsequent level? Like every other class?

[StabbittyDoom]

joeyfixit wrote:

Huh? Why wouldn't it be 10+Con for the first hit die, 6+Con for every subsequent level? Like every other class?

You only maximize your first hit die if it's from class. If your first hit die is gained from race, you never get a maximized hit die.

(This is a slightly less well known rule amongst players as they are almost always in the "first hit die is from class" camp.)

[Tar-Tar]

SRD wrote:

The following information is not official in terms of general campaign usage. It is copied from the Pathfinder Society Organized Play FAQ section because we thought it might be helpful information for a player or GM in adjudicating common problems or questions. Usage is up to the GM of your game.

How do I determine hit points for my animal companion?

Animal companions receive average hit points per hit die. For d8, the average is 4.5. Multiply 4.5 times the number of hit dice your animal companion has and round down. Recalculate hit points for your companion each time it gains additional hit dice. After its hit points are calculated, add in appropriate bonuses from its Constitution modifier, feats, and so on.

And this is a sample animal companion. It has average hit points for each hit di, including first. True, it's not an eidolon, but I think the same thing applies.

Also,

SRD FAQ wrote:

Creatures whose first Hit Die is from a PC-appropriate character class gain max hit points for that Hit Die. The current list of PC-appropriate character classes is alchemist, barbarian, bard, cavalier, cleric, druid, fighter, inquisitor, monk, oracle, paladin, ranger, rogue, sorcerer, summoner, witch, and wizard (including archetypes, subclasses, and other variants of these classes).

Creatures whose first Hit Die is from an NPC class (adept, aristocrat, commoner, expert, warrior) or from a racial Hit Die (such as most monsters) do not get maximum hit points for that Hit Die. All creatures with class levels (including those with levels in an NPC class or monsters with class levels) may select a favored class and gain the normal favored class benefits. Creatures never gain favored class benefits for racial Hit Dice. For example, a human warrior 1 could select "warrior" as his favored class and take either the bonus hit point or skill rank for taking a level in that class. A normal bugbear with 3 racial Hit Dice and no class levels has no favored class and no favored class bonuses, but if that bugbear gained a level in rogue, he could choose "rogue" as his favored class and take either the bonus hit point or skill rank for taking a level in that class.

I don't like this particular rule all that much, but that's just me. Well, me and anyone with an animal companion/eidolon/mount.