The black Chrom starting off with a Killing Edge represents Lon'qu, a Mercenary who wears a dark-colored tunic and wields a Killing Edge in battle.
The stage is based on Arena Ferox in the fourth chapter of Fire Emblem Awakening, which first features Lon'qu as a party member.
Other trivia:
This spirit's Support type references Lon'qu's role as a member of Chrom and Robin's party in Awakening.
This spirit's Attack type and Killing Edge Equipped ability further reference how Lon'qu is armed with the Killing Edge.
