Favour and Slight are used to adjust the probabilities of success, without affecting the possible range of outcomes. They are best used when situations would aid or hinder a character's actions.

When a 2d10 roll is made with favour, the player rolls one additional d10, and then discards the lowest among the dice. Favour stacks; if a character has multiple instances of favour that apply, they roll an additional d10 for each instance of favour, and discard one die for each instance of favour.

When a 2d10 roll is made with slight, the player rolls one additional d10, and then discards the highest among the dice. Like favour, slight stacks; if a character has multiple instances of slight that apply, they roll an additional d10 for each instance of slight, and discard one die for each instance of slight.

Favour and slight cancel each out. So if a character has three instances of favour and one of slight on a single roll, the roll is made with two instances of favour.

Favour and slight have diminishing returns. While the first instance of favour is worth about the same as a +3 (in terms of chance to roll into the higher success bands), additional instances have a reduced effective bonus. And regardless of how many instances of favour or slight a character has, the maximum or minimum that they can roll is unchanged.