|“||Rain down arrows from above at the opponent Rex strikes. This Final Smash has less launch power than Pyra's, but it deals high continuous damage in a wide area.||”|
|—Description from Ultimate's Move List.|
Once activated, Rex will be summoned and performs a wide underhand slash of the Aegis while yelling 'Mythra, now!". If any fighters are caught, it will then transition to a brief cutscene where Mythra and Rex will hold the Aegis together and aim it directly towards the sky to summon a beam of light while shouting the move's name. It then cuts back to normal gameplay view, where a series of energy bullets begin to rain on the trapped opponents. It then ends with the two aiming the Aegis towards the fighters and firing one final beam at them. Rex then disappears once the attack has completed.
In comparison to Pyra's Final Smash, Burning Sword, though strong on its own right it is more intended to build up damage percentage. Much like Burning Sword, the move can only trap up to three opponents; however, the rain of bullets can attack any other nearby characters and potentially KO them as well.
Sacred Arrow is Mythra's Level IV Blade Special in Xenoblade Chronicles 2; the in-game description describes the move as "Rain down arrows of light from above to tear the enemy apart". Its depiction in Smash is an exact recreation of the original save for the trapping slash at the beginning, which is an original addition. It also lacks the original's unique condition of prevented use if a battle took place indoors.
|Mythra's Special Moves|
|Standard Special||Lightning Buster|
|Side Special||Photon Edge|
|Up Special||Ray of Punishment / Chroma Dust|
|Down Special||Swap to Pyra|
|Final Smash||Sacred Arrow|