If a synthetist is fused with his eidolon (and thus cannot be targeted by spells) and a fireball is cast around him, who takes damage?
When they are fused they are one creature. The synthesis gains the eidolon’s HP as temporary HP. Temporary HP are used first until they are gone. When the temporary HP are gone the eidolon is killed and sent back to its own plane.
Treat them as though they only have one hit point pool while fused, with the ability of the summoner to sacrifice hp to prevent damage to eidolon that's basically how it works.
They don't both take damage if that's what you were curious about.
Im also curious about other aswell. Example: How would you cast Bull Strength on them while they are fused?
If the synthetist uses the eidolon's str score, and the eidolon cannot be targeted by spells, that means it's impossible? Or that, being a single creature, the synthetist gains the effects of the spell normally?
Im also curious about other aswell. Example: How would you cast Bull Strength on them while they are fused?
If the synthetist uses the eidolon's str score, and the eidolon cannot be targeted by spells, that means it's impossible? Or that, being a single creature, the synthetist gains the effects of the spell normally?
They are counted as a single entity for purposes of spells.
Summoner: What happens when a synthesist (page 80) takes a penalty, suffers an affliction, or has an ongoing effect when the eidolon disappears?
These effects persist on the summoner after the eidolon is gone. For example, a ray of enfeeblement on the fused character continues to affect the summoner after the eidolon is gone, as would a bestow curse spell or acid arrow spell, as would continuing poison damage. These effects apply to the character as a whole, and just because the eidolon is gone doesn't mean the summoner is freed from the effect (ability damage is tracked separately, as described in another FAQ, because it is a separate game statistic that the summoner "borrows" from the eidolon). If the condition or effect ends (whether from its duration running out, being cured/negated/dispelled, and so on) while the eidolon is gone, it doesn't return when the eidolon is resummoned. This applies to beneficial effects as well as harmful ones--an invisible summoner isn't suddenly visible if his eidolon disappears, nor does he become invisible again if the duration ran out while the eidolon was gone.
The benefits are applied normally, and remain in effect if the eidolon goes away. Bull's Strength, for example, will enhance the current strength of the fused summoner/eidolon. Should the eidolon go away, Bull's Strength will continue to enhance the summoner, using the summoner's unfused stat.
@Snowlilly. How about when the synthetist is affected by Linnorm Death Curse and his eidolon hits 0 hit points and dies? Does the eidolon's death trigger the death curse?
Eidolons can't die -- they can only be banished for 24 hours. So the "death" of an eidolon would not trigger a death curse.
@Snowlilly. How about when the synthetist is affected by Linnorm Death Curse and his eidolon hits 0 hit points and dies? Does the eidolon's death trigger the death curse?
Per the wording of Fused Eidolon, a synthesists eidolon is killed and sent back to it's home plane when it reaches 0 temporary hit-points.
Since fused eidolon specifies the eidolon is killed at 0 temporary HP:
1. The linnor death curse triggers
2. Per FAQ, the summoner will continue to be affected by the linnorn death curse rage power.
Starting at 1st level, the synthesist forms a close bond with his eidolon. Whenever the temporary hit points from his eidolon would be reduced to 0, the summoner can, as a free action, sacrifice any number of his own hit points. Each hit point sacrificed this way prevents 1 point of damage done to the eidolon (thus preventing the loss of the summoner’s temporary hit points), preventing the eidolon from being killed and sent back to its home plane.
Emphasis mine.
@Snowlilly
That's assuming the curse triggers before the synthetist meld ability. According to the FAQ, whenever the eidolon dies, any lasting effect on the synthetist (that affected both as a single creature) passes on to the summoner.
From what i can see, none of those abilities is more specific than the other, so they have a similar scope. How to decide which one happens first?
By RAW the eidolon is killed.
That meets the trigger condition for linnorn death curses.
If the character is knocked unconscious or killed by an attack or spell
Emphasis mine.
The same wording is used for both the eidolon and the linnorn death curse.
If you think this is cheese, consider the skald could also be conjuring stirges, which would benefit from the death curse.