Disadvantage
Term
Sometimes when a 
Challenge Roll is made, the rules or the GM might require a roll to be made at Disadvantage ( DIS).
This means two d20s are rolled, and the LOWER of the two rolls is taken before summing modifiers or another adjusting rolls.
Example: Making an Attack Roll a creature behind cover. Making a 
Contesting Roll but under the curse of a 
Warlock.
d100
Mod
ADV/DIS