
Lavode de'Morcaine |

My GM let me do this last session. But now we're not really sure if it should have worked.
Creature we are trying to talk to.
None of us speak the correct language.
Stupidly, none of us have replenished our supply of scrolls of Tongues or anything like that.
I cast Oracle's Burden so that it could only speak celestial and we could communicate.
Should this have worked?

Nothing |
The key phrase is:
The target creature suffers all the hindrances and none of the benefits of your oracle's curse class feature.
So it would gain the hindrance of only being able to speak or understand Celestial while in combat without the benefit of having Celestial as a bonus language.
So by RAW it appears that if the target didn't already understand celestial, they would not be able to speak or understand any language while in combat, and outside of combat it would have no effect.

Nothing |
Bigdaddyjug, I imagine something like this:
1) Party meets creature they can't talk to.
2) Oracle casts Oracle's Burden on creature, which is an offensive spell and starts combat.
3) Creature is in combat and can now understand celestial, (although it shouldn't understand any language as I stated above), and attacks the Oracle.
4) Oracle casts Charm Monster, creature fails save (with +5 bonus for being in combat).
5) Still in combat, Oracle commands creature to spar with him (fighting defensively, dealing non-lethal).
6) Everyone can still speak as they fight, Oracle asks questions and creature answers in celestial as they miss each other or occasionally deal non-lethal.
7) When done, Oracle asks creature to stand still for a minute before going home and acting as if the last 20 minutes never happened for the rest of the spell's duration.
8) Combat ends, Oracle heals creature.
9) Creature goes home, happy to have met a new friend for the next week or two, then hates the Oracle's guts and sets out to kill the manipulative bastard.
All perfectly legal except for step 3.

Lavode de'Morcaine |

Actually pretty durn close. Except...
4) Paladin/bard uses a magic item flute that casts charm monster
5) Ranger slaps creature around while oracle talks to creature and paladin bard continues playing flute.
7) Creature fails save vs fear from surprise mummy attack and flees into the swamp.
And yes, it probably hates us now. But I think if we manage to rescue and return it's child, it will probably forgive us.

Splendor |
Oracle's Burden
You entreat the forces of fate to bestow your oracle's curse upon another creature. The target creature suffers all the hindrances and none of the benefits of your oracle's curse class feature.
Tongues
In times of stress or unease, you speak in tongues.Effect
Pick one of the following languages: Abyssal, Aklo, Aquan, Auran, Celestial, Ignan, Infernal, or Terran.
Whenever you are in combat, you can only speak and understand the selected language. This does not interfere with spellcasting, but it does apply to spells that are language dependent. You gain the selected language as a bonus language.
From the description the curse kicks in under stress or unease, not just combat. However it always kicks in when in combat.
The enemy was possibly being threatened and having spells cast upon it, it could easily have been uneasy.
Since it only gains the hindrance and not the benefit of the oracle's curse, it wouldn't be able to speak intelligently inside or outside of combat.
Which actually makes this a pretty good offensive spell against wizards. Pick one of the languages that most don't speak (like Aklo or Auran) and if the enemy wizard can't speak in that language he can't cast any verbal spells (To cast a spell, you must be able to speak).

Lavode de'Morcaine |

...
Quote:Tongues
In times of stress or unease, you speak in tongues.Effect
Pick one of the following languages: Abyssal, Aklo, Aquan, Auran, Celestial, Ignan, Infernal, or Terran.
Whenever you are in combat, you can only speak and understand the selected language. This does not interfere with spellcasting, but it does apply to spells that are language dependent. You gain the selected language as a bonus language....
Which actually makes this a pretty good offensive spell against wizards. ... if the enemy wizard can't speak in that language he can't cast any verbal spells (To cast a spell, you must be able to speak).
Nope.

Splendor |
One
Oracle's Burden says that the target of the spell gets none of the benefits of your oracle's curse class feature.
One of the benefits of the class feature is the ability to speak celestial.
If you can't speak a language you can't cast spells.
Two
"not interfere with spellcasting" could easily be interpreted as a benefit of the oracle curse and since Oracle's Burden doesn't grant you any of the benefits of the curse, the target wouldn't get this one either.