[PF] How does the Synthesist work?

[RndmNumGen]

I've started working on a character concept where a noble woman tried to sacrifice her newborn child to a devil for power, but messed up the ritual and ended up killing herself and binding the devil to the child instead, forcing thw two to share one body. After looking at the PFSRD, Synthesist seems like a very fitting option for this. However, I'm having difficulty figuring out exactly how it works - the rules and exceptions surrounding it seem to be incredibly byzantine.

So when I summon my Eidolon, I get Temporary HP equal to what the Eidolon's HP would be. Once this HP is depleted however, is it ever possible to get it back? Life Link only works for preventing damage, and even then only when the Eidolon is almost dead. I can't use Cure spells to heal Temporary HP, and the Eidolon doesn't heal naturally. When I summon the Eidolon, it's HP is equal to what they were when it was last dismissed. So how does it heal?

The second thing is ability scores. By my understanding, calling the Synthesist's Eidolon acts more like Polymorph than an actual Summon Monster spell. But what about feats? If I only have 8 STR, but my Eidolon has 16, can I qualify for Power Attack(Since my Eidolon doesn't get feats?)

Then there are also weapons and weapon proficiencies. Natural attacks seem to work okay, but do I still retain use of whatever weapon proficiencies I have while in Eidolon mode, or do I need to spend an evolution on the proficiencies?

I think I get how magic items work - they affect both my Eidolon and myself, but the benefits don't stack(So basically, I always benefit from magic items, regardless of the form I'm in, but only benefit once, not twice).

That's just the stuff on the surface... I'm sure there are other nuances I haven't even noticed yet. Is there some sort of guide somewhere that breaks this down?

[Crasical]

So when I summon my Eidolon, I get Temporary HP equal to what the Eidolon's HP would be. Once this HP is depleted however, is it ever possible to get it back? Life Link only works for preventing damage, and even then only when the Eidolon is almost dead. I can't use Cure spells to heal Temporary HP, and the Eidolon doesn't heal naturally. When I summon the Eidolon, it's HP is equal to what they were when it was last dismissed. So how does it heal?

When your Eidolon is killed, it always returns with half HP, so a Synthesist Eidolon returns with half temporary HP. Spells like Rejuvinate Eidolon can also patch it up (http://paizo.com/pathfinderRPG/v5748btpy8k8r/faq#v5748eaic9ob8).


The second thing is ability scores. By my understanding, calling the Synthesist's Eidolon acts more like Polymorph than an actual Summon Monster spell. But what about feats? If I only have 8 STR, but my Eidolon has 16, can I qualify for Power Attack(Since my Eidolon doesn't get feats?)

I tend to go with the interpretation that since you can wear the Eidolon for as long as you want (except when asleep), it qualifies as a permenant bonus and allows the PC to take Power Attack, with the feat only functional when the Eidolon is summoned.


Then there are also weapons and weapon proficiencies. Natural attacks seem to work okay, but do I still retain use of whatever weapon proficiencies I have while in Eidolon mode, or do I need to spend an evolution on the proficiencies?
You retain the use of whatever you personally are proficient in.

[grarrrg]

How does the Synthesist work?
Poorly.
*rimshot*


So when I summon my Eidolon, I get Temporary HP equal to what the Eidolon's HP .....So how does it heal?

As mentioned, the Rejuvinate Eidolon line of spells still work.
Also, it's a fairly simple houserule to allow Cure-X to heal it as well.


The second thing is ability scores. By my understanding, calling the Synthesist's Eidolon acts more like Polymorph than an actual Summon Monster spell. But what about feats? If I only have 8 STR, but my Eidolon has 16, can I qualify for Power Attack(Since my Eidolon doesn't get feats?)

Yes, and No.
If you have a Temporary bonus for 24+ consecutive hours it counts as a 'permanent' bonus (so long as you still have the bonus).
But once you 'rest' the Eidolon goes away, so "technically" you can just stay awake (and be exhausted/fatigued) for a few extra hours, wait until they become "permanent" and then choose to Level up. But that could be considered extreme Meta-Gaming.
Ask your DM.
If you CAN qualify for feats with Eidolon stats, then keep in mind that they may 'turn off' when/if you revert to normal form.


Then there are also weapons and weapon proficiencies. Natural attacks seem to work okay, but do I still retain use of whatever weapon proficiencies I have while in Eidolon mode, or do I need to spend an evolution on the proficiencies?

Proficiencies are Feats, you retain all of your feats in Eidolon form (subject to maintaining the per-requisites as above).


I think I get how magic items work - they affect both my Eidolon and myself, but the benefits don't stack(So basically, I always benefit from magic items, regardless of the form I'm in, but only benefit once, not twice).

For the most part yes, there are still gray areas regarding Armor and such, but each Item can only effect you once.


That's just the stuff on the surface... I'm sure there are other nuances I haven't even noticed yet. Is there some sort of guide somewhere that breaks this down?

No. Not for the Synthesist there isn't. Use common sense, your DM, and this forum.

[Keneth]

For the most part yes, there are still gray areas regarding Armor and such, but each Item can only effect you once.
You don't benefit from armor because the eidolon can't use armor. But that's pretty much irrelevant because your natural armor is gonna scale fast enough to give you plenty of AC, the only drawback is that you can't have armor special abilities.

[RndmNumGen]

When your Eidolon is killed, it always returns with half HP, so a Synthesist Eidolon returns with half temporary HP. Spells like Rejuvinate Eidolon can also patch it up (http://paizo.com/pathfinderRPG/v5748btpy8k8r/faq#v5748eaic9ob8)
I see. Useful to get a wand of that, given the limited number of spell slots a summoner has. What if the Eidolon has, say, the Fast Healing evolution? Would that heal the temp HP, or would it essentially be ineffective?

[Crasical]

I see. Useful to get a wand of that, given the limited number of spell slots a summoner has. What if the Eidolon has, say, the Fast Healing evolution? Would that heal the temp HP, or would it essentially be ineffective?

Per that link I gave you, Fast Healing or Regeneration, be it from evolution or some other place, restore your HP, not the Eidolon's temp HP.