Goat format ruling
Mirage of Nightmare

Card effect (current official text)Once per turn, during your opponent's Standby Phase: Draw cards until you have 4 cards in your hand. If you do, during your next Standby Phase after that: Randomly discard the same number of cards you drew (or your entire hand, if you do not have enough cards).
Rulings
- If, after drawing during your opponent’s SP, your Mirage of Nightmare is destroyed before you have to discard, then you do not need to discard for its effect.
- When the turn player controls Mirage of Nightmare and Imperial Order: If you draw for Mirage of Nightmare during your opponent’s SP, and then activate Imperial Order after that, during your SP you will have 2 mandatory effects: discarding for Mirage of Nightmare and paying 700 LP for Imperial Order or else destroying it. In this case, you choose which effect to resolve first, and you can choose to resolve Mirage of Nightmare first, even though its effect will be negated by Imperial Order. So you activate its effect, and do not discard. Then you can choose not to pay 700 LP to keep Imperial Order, and Imperial Order will be destroyed. Then you can enter MP 1, and you did not have to discard for Mirage of Nightmare (because its effect was negated at the time you chose to resolve it). (Seach for Mirage of Nightmare 2 to continue reading)
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Goat forum — sourced change requests get reviewed.