This skill covers everything from staring somebody down (WP) to the veiled threats of the Empire's courts (Soc). Generally a contested roll of WP or Soc/Intimidate is made against the target's WP/Intimidate.
Failure means that you may have offended someone that you didn't want to, or that your threat was simply hollow. Future attempts to intimidate will be at - 1 die. Success causes the target of the intimidation to give in some way. One success may be a flinch or soft concession while five calls for a change of pants.
Those in no position to intimidate (peasants in the face of royalty in the palace, paraplegics, etc.) will suffer die penalties, at the Seneschal's option. Other factors, such as size, magic, or obvious superiority in strength, power, social standing or whatever may grant additional dice or lower Target Numbers.
The exact effects of intimidation are up to the Seneschal, though penalties to dice pools and attributes may be appropriate in many situations.