Chaos Dragon

An ability that tells you to roll a die will also specify what to do with the result of that roll. Most often, this is in the form of a "results table" in the card text.

Dice used must have equally likely outcomes and the roll must be fair. Although physical dice are recommended, digital substitutes are allowed, provided they have the same number of equally likely outcomes as specified in the original roll instruction.

Tournament events have more specific rules regarding dice and die-rolling. For more information, please see the most recent version of the Magic Tournament Rules at https://wpn.wizards.com/en/document/magic-gathering-tournament-rules.

You roll a d20 as well as your opponents. If you had a higher result than all of your opponents, Chaos Dragon won't have any restrictions on who it may attack.

The instruction to roll a die and the effect that occurs because of the result are all part of the same ability. Players do not get the chance to respond to the ability after knowing the result of the roll.

Dice are identified by the number of faces each one has. For example, a d20 is a twenty-sided die.