Minions of underfoot faction.
 

Can bard song and/or clicky necklace make non brell worshippers non kos to these?

Apparently the rats are on this faction but I swear I was there once and got attacked on my dwarf. Is there a rat that's not on this faction?

Yes most combos start as Glares and can raise it to dubious with spells and illusions. Rats and undead are on their own faction and impossible to raise

I thought rats were seperate but it says minions of underfoot on the wiki, is it wrong?

I can confirm rats, ghosts and Master Yael are all kos to Brell worshipers who have never taken a faction hit to Minions of Underfoot. Elementals, rock golems and imps are non-KOS. I cannot confirm though if you take a minions faction hit killing a rat though.