I was curious if there is a Domain, Magic Item, Trait, Feat, or something that might help to increase the damage inflicted for a negative channeling Cleric. Ya know, something like 1d6+1, and then it continues to increase a bit as the character levels. I know theres a small bonus for positive channelers vs. Undead like that.
Again, must be PFS legal.
It takes up your headband slot so no Wis/Cha headbands but you can get an Ioun Stone for 8k of the stat you need to partially make up for that and there is a specific high tier scenario that grants a unique amulet with your choice of Wis or Int at a +4, with an option to upgrade to a +6. So if you're a Cleric that necklace is an option for you to keep your spell DCs up.
Also note that the Cleric (Variant Channel) archetype is legal for PFS play. None of these increase damage, but some substitute an alternate effect instead of the 50% of damage targets can otherwise save against. Noteworthy deities are Horus (Rulership), Dispater (Rulership), and Fandarra (Earth). Also note that negative Variant Channel effects apply at full strength even when used by the secondary channel of Versatile Channeling.
One of my friends used a variant channeling build worshipping urgothoa for pfs. On every channel, unless every target made a cha based high willsave they became shaken. This effect however stacks with itself. After the second channel, they are frightened and effectiveky become non-combatants, only concerned with running away. Also, every channel.could affect one target with a disease. You could use bubonix plague for permanent blindness or mindfire to deal int damage. Most animals and worms etc have low int and can thus be one-shot by this channel ability.
It was extremely powerful and could blow up.encounters even better than a wizard. The only downside is that your wis.score will be lower than mosy clerics and your bonus spells will suffer a bit.
If you don't mind being empty after a couple of rounds only, I might also suggest Quick Channel. Not exactly what you might seek, but it nicely raises the output. Otherwise, Improved Channel to raise the channel DCs. Outside of the phylactery though, I couldn't see which item could raise the damage per channel *sheepish*