What does Ancestral Communion allow you to do exactly?

[Berry Buiten]

PFSRD wrote:

Ancestral Communion
School divination; Level bard 2, cleric/oracle 2

CASTING

Casting Time 1 minute
Components V, S, F/DF (stone or metal image of your ancestor)

EFFECT

Range personal
Target you
Duration 1 minute/level

DESCRIPTION

You contact the spirits of your ancestors and use their great wisdom to bolster your own knowledge. Consulting with the spirits is a full-round action. If you consult with the spirits before making a Knowledge check, you gain a +4 insight bonus on the check. If you have already failed at a Knowledge check, you may consult with your ancestors and make another attempt. The insight bonus on these checks increases to +6 at caster level 7th and +8 at caster level 11th. You may consult with the spirits for this purpose as often as you like while the spell remains in effect. Only you can hear the spirits speak to you.

It seems to me that it says for sure that:

1) You can reroll failed Knowledge checks.
2) You can do so with the appropriate bonus.
What I also read, the bolded part, but seems way too powerful:
3) You can try again and again for as long as the spell lasts. Basically allowing you to take 20?

Your opinion?

[avr]

It takes a minute to cast the spell and a full round action each time you consult the spirits. It's powerful but limited - the spell's basically incompatible with combat, and also impossible to use in many social situations or other situations where you can't take a minute out to think about it, or probably even in research where the 1 minute/level duration isn't long enough to cover the skill check (mileage may vary on whether that's necessary). Oh, and bards are often short of spells known and spell slots, and clerics and oracles are often short of skill points.

[Berry Buiten]

Aaah okay, that seems much more reasonable!

[Berry Buiten]

Yeah, looking a bit deeper using Google-fu I found a spell that actually grants you a 20 as a full round action. So for a standard action and a full round action you know as much as Ancestral Communion gives you after an average of three minutes.

I guess I overreacted :)

https://www.d20pfsrd.com/magic/all-spells/h/hunter-s-lore/

[Belafon]

Like the vast majority of spells it's not an "automatically awesome" spell but may be useful depending on your particular campaign and character.

I played a Scroll Scholar cleric in PFS for a long time, and ancestral communion was quite good in that setting. Most scenarios start with a bunch of knowledge checks to get information that will be helpful later on. If I flubbed a check (and no one else did better) I would spend 15 minutes meditating to put ancestral communion in an open slot and try the check again.

[Mysterious Stranger]

The spell does not allow you to make knowledge skills you would not already be able to make. That means it is only effective on knowledge skills you are trained in. Keep in mind that unless you are trained in a knowledge skill you cannot make a roll for something that has a DC higher than 10.

The spell can only be used by someone casting from the bard or cleric spell list. Most casters using the cleric spell list don’t have a lot of skill points and for the most part don’t have all knowledge skills as class skills. This is going to limit how much use they can get out of the spell.

Bards have all knowledge skills as a class skill and can use them untrained. But bards get Lore Master so can already take 20 on knowledge skills anyways. Bards also get a bonus of ½ their level on all knowledge skills. Between these abilities bards already have a huge advantage on knowledge skills. In all honesty this spell is probably overkill for a bard. Considering their limited number of spells they would be better off choosing heroism instead.