Anyone can challenge a disguised set during their turn, and their opponent must reveal it.
If the opponent is bluffing, they will lose all their sets and full hand to the bottom of the discard pile, then pick up one card from the pylon. If they are not bluffing, the challenger will have to do the same.
If you lose a challenge you will pitch your cards underneath the discard pile
A player can’t have their disguised set challenged once they signal “Omaha.” Disguised sets will remain faced-up once challenged, and players can use them for hitting.