I've always loved the bardic knowledge ability but disliked the class (and the loremaster too for that matter). This is great, thanks. The only change I would make is to change the check to ranks in gather info plus int minus 5, so that is would be two levels weaker than a bard. As is, you can be better than a bard 3 levels higher than you with only a feat.
Requirements: Knowledge (local) 4 ranks in the chosen location, Gather Information 4 ranks, Listen 2 ranks, Charisma 12.
You possess the bardic knowledge ability when in the chosen location. This location is restricted to a city sized area.
As a rumormonger, you may attempt to use bardic knowledge by substituting your ranks in gather information for bard levels. Your check will be equal to your ranks in Gather Information + your Intellegence modifier.
If you are also a bard, before attempting to use bardic knowledge you may also declare that you are using the Rumormonger special ability. If you do, add half of your ranks in Gather Information to your bard level when making a bardic knowledge check; that is, your bonus is your bard level + half the number of ranks in Gather Information + your Intelligence modifier.
Furthermore, an additional bonus is granted to common information: A check at DC 10 gets a bonus of +3, a check at DC 15 gets a bonus of +2 while a check at DC 20 gets a bonus of +1. The DC of any check should be made relative to the rarity of that information in the chosen location.
The drawback, however, is that the information gained by Rumormonger may not be correct (even information gained through use of the bardic ability in conjunction with Rumormongering). After declaring that you are using Rumormonger, the bardic knowledge check is made secretly by the DM. If it fails, the DM will provide false or inaccurate information; how false or inaccurate is entirely at the DM's discretion. There is absolutely no way for you to distinguish between true and false information gleaned by using this feat.
You may also attempt to spread rumors with a Gather Information check. This takes one full day during which you may not do anything else except eat and sleep, and requires full, unfettered access to the region (i.e. you can't be in jail). The DC associated with a given rumor is determined as follows:
The more specific the rumor being spread, the higher the DC. In general, each additional increment of specificity should raise the DC by 5; thus, if it's important not just that the plague is coming, but specifically that the red-veined bloodscourge is coming on the Great Eastern Caravan Route, the DC check of this rumor should be 30, not 20.
If the check succeeds, the rumor will spread throughout the region within 1d6 + 1 days. You may spread up to 3 rumors per week. For each rumor beyond the first, however, you incur a cumulative -2 penalty on the Gather Information check as you are testing the limits of believability; hence the second rumor spread in a week is at a -2 penalty, and the third rumor is at a -4 penalty.
Optional rules At the DM's discretion, depending on how baroque you want to get: