??? can refer to the following units:
???: Masked Knight, a 
Cavalry 
Blue Tome user who appears in Fire Emblem Heroes.
???: Near and Dear, a Infantry Sword user who appears in Fire Emblem Heroes.- ???: Summoned One, a Infantry Sword user who appears in Fire Emblem Heroes.
or the following characters during certain story scenes:
- Henriette
- Hvergel
- Arthur: Hapless Hero
- Askr: God of Openness
- Balthus: King of Grappling
- Bartre: Fearless Warrior
- Byleth: Tested Professor
- Charlotte: Wily Warrior
- Dimitri: Savage Boar
- Eitri: Youthful Sage
- Elimine: Scouring Saint
- Embla: God of Closure
- Fáfnir: King of Desolation
- Fáfnir: King of Desolation
- Faye: Devoted Heart
- Fjorm: Ice Ascendant
- Freyja: Lady of Nightmare
- Ganglöt: Death Anew
- Ginnungagap: Ruler of Nihility
- Gullveig: Golden Seer
- Gunnthrá: Voice of Dreams
- Hel: Death Sovereign
- Laevatein: Ninja of Múspell
- Letizia: Curse Director
- Líf: Lethal Swordsman
- Loki: The Trickster
- Lucina: Brave Princess
- Lucina: Future Witness
- Marth: Enigmatic Blade
- Micaiah: Summer's Dawn
- Mirabilis: Daydream
- Múspell: Flame God
- Nifl: Tropical Ice God
- Niles: Cruel to Be Kind
- Nils: Bright Bard
- Nina: Eye Spy
- Ninian: Bright-Eyed Bride
- Norne: The Volunteer
- Nyx: Rulebreaker Mage
- Peony: Sweet Dream
- Perne: Dacian Scoundrel
- Plumeria: Lewd Dream
- Seiðr: Goddess of Hope
- Setsuna: Absent Archer
- Sharena: Princess of Askr
- Thrasir: Omnicidal Witch
- Tiki: Awakened Blood
- Triandra: Nightmare
- Wrys: Kindly Priest
- Xane: Desert Mirage
- Ymir: Life-Mother
or the English and Japanese voice actors of:
or Tap Battle final stage boss previews: 
Sigurd: Holy Knight, 
Tharja: Dark Shadow.