I loaded a save at the end of chapter 2, boosted the dwarves' opinion and got a lizard's faction decision the next turn. Denying it got the dwarves' faction decision for the next political choice, but they would have been at 85% even without Corvus' help. Reloading again and always going against the dwarves, with 4 or 5 visits to Corvis, they did not bring up a faction decision from turn 37 to 112.
