Common Eidolon Questions:
1. Does the Monster feat “Improved Natural Attack” and the Eidolon Evolution “Improved Damage”, stack?
Paizo Forum Post – A summary of both rules (in the first post), and some considerations in interpreting the rules.
My conclusion: Both the feat and the evolution say “increase die by one step”, which means they don’t stack. However, you CAN cast Enlarge Person on your Eidolon, and that WILL stack.
2. Can you have both a slam attack and claws on the same limbs(arms)?
Paizo Forum Post (inconclusive)
Another Paizo Post (some good thinking)
My conclusion: No. Also, the Slam takes both arms to use, so you also can’t Claw+Slam with the same pair of limbs(arms), even if you buy more Claws.
3. The conclusive FAQ from paizo about claws on feet for bipeds. The short answer is “no”.
4. Does Augment Summoning affect your Eidolon? What if you summon your eidolon with the spell Summon Eidolon?
The short answer is “no”. The short reason is “game balance”.
5. Does Augment Summoning work with the Summon Monster Spell-like Ability?
Yes. It was confirmed by paizo’s game designers.
6. Can you have a Summon Monster from SLA and your Eidolon in play at the same time?
Maybe. By the wording, you can use your SLA without your Eidolon, and then use the Summon Eidolon spell to summon your Eidolon, but not the other way around. However, it’s also stated that the power to summon your Eidolon is the same power that is used for the SLA, although this is not explained in much detail, so it might be a flavour-reason. So… it’s basically up to your DM’s interpretation of these rules.
As a DM, I encourage you NOT to allow it, for balance reasons. Summoners are powerful enough already! (I also encourage you to look at the Unchained Summoner variant, which reduces their power in line with other classes)
The possible reason that you can use your SLA and THEN your Summon Eidolon spell is that:
a) A summoner’s spells known is very limited
b) A summoner’s daily allotment of spells isn’t that good either.
Thus, my thought is that if the summoner wants to spend his limited resources and choices on being able to do both, he should be allowed to. It also forces him to go at least the first round of combat without his Eidolon, assuming the combat starts without “buffing time”.
As a side note, the proper way to do this is: do NOT have your Eidolon summoned. Use your first standard action to cast your SLA as a Standard Action, which allows the Summoned Monster to full-attack that round, assuming you summon it adjacent to an enemy. Next round, cast your Summon Eidolon spell as a Standard Action, which allows your Eidolon to attack that turn, as well. If you are in the habit of walking around with your Eidolon out, your first Standard Action will be to dismiss the Eidolon after it has attacked, then next round cast your SLA, then the 3rd round, re-summon your Eidolon. However, I don’t think this is very practical, as you’re missing out on opportunities to cast other spells, such as Grease, Haste, Create Pit, and Black Tentacles, which are amazing spells.