You can make (up to) one disguised set by placing a set face down to hide from your opponent. Your disguised set has to have all cover cards to be legit, and an opponent can challenge it. Once downed, a player can not add cards to it. You must have at least three cards left in your hand at the end of the same turn you created a disguised set; otherwise, you can’t create it. You can acquire a second disguised set from an opponent.
You can set these covers face down to make a legit disguised set.
If you make a face up cover set then you can add cards to it like normal.
You are bluffing a disguised set if any of the cards are not covers or wildcats.
Both of these sets are bluffs. Wildcats can be substituted in place of covers.
You can taunt players (anytime) by flipping any of your disguised set cards face up, but one has to remain face down.