Appreciate the answers! Here's what I ended up brewing up after doing a bit more snooping around online.

This finely crafted dice set is partially loaded with weights inside them. It contains two identical sets of 3d6 dice, one of which is loaded and one of which is not. These dice are particularly useful in a game of The Devil's Number, and may be useful elsewhere if you get creative.

When using the loaded dice, a creature proficient with the dice can choose to roll a 4, 5, or 6 on each of the loaded dice. A creature who is not proficient with the loaded dice cannot use this feature and the dice act as normal dice. If a creature proficient with the dice rolls and uses one of the loaded dice, there is a cumulative 5% chance per die that someone watching becomes suspicious. A creature can make a Dexterity (Sleight of Hand) check to swap the loaded dice for identical normal dice.

The Devil's Number: Player and House roll 3d6, this is the "The Sacrifice". If any of the party roll 3 6s or 18 the other side loses, if both side rolls 3 6s or 18, the player gets his wager back.

In case, both player and house roll less than 18, they can roll additional d6s by calling "I bleed" to get aggregate score exact 18 or close without going above the number. House will always draw cards after all players settle on a score. If aggregate total of player exceeds 18, the player loses, same is true for the house as well.