Mordor on the March

• WOTC Official Reminder Textofficial rules
  Storm — When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.

• WWizards of the Coast2023-11-03
  Official Ruling
  Any enters-the-battlefield abilities of the copied creature card will trigger when the token enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the copied creature card will also work.
• WWizards of the Coast2023-11-03
  Official Ruling
  Spells cast from zones other than a player's hand and spells that were countered or otherwise failed to resolve are still counted by the storm ability.
• WWizards of the Coast2023-11-03
  Official Ruling
  If Mordor on the March creates multiple tokens due to a replacement effect (such as the one Doubling Season creates), each of those tokens will gain haste, and you'll exile each of them at the beginning of the next end step.
• WWizards of the Coast2023-11-03
  Official Ruling
  The token copies exactly what was printed on the original creature card and nothing else.
• WWizards of the Coast2023-11-03
  Official Ruling
  If another creature becomes a copy of, or enters the battlefield as, a copy of the token, that creature will copy the creature card the token is copying. However, the new copy won't gain haste and you won't exile it at the beginning of the next end step.
• WWizards of the Coast2023-11-03
  Official Ruling
  A copy of a spell can be countered like any other spell, but it must be countered individually. Countering a spell with storm won't affect the copies.
• WWizards of the Coast2023-11-03
  Official Ruling
  The copies of Mordor on the March created by its storm ability are put directly onto the stack. They aren't cast and won't be counted by other spells with storm cast later in the turn.
• WWizards of the Coast2023-11-03
  Official Ruling
  If the copied creature card has in its mana cost, X is 0.

Rulings via Scryfall