Most Mythical Pokémon had others of their kind. Marshadow's kind was different from all the rest.
Ho-Oh had created Marshadow by fusing its own shadow with life energy. So while there was technically more than one Marshadow, only one existed in the world at a time. In a sense, each was unique.
Once six hundred years passed, the current Marshadow would return to Ho-Oh's shadow, and a new "Marshadow" would be born—identical in appearance, but with an entirely different consciousness.
Only then did Ye Lan realize that Marshadow's six-hundred-year cycle closely matched Ho-Oh's six-hundred-year rebirth. Perhaps Marshadow's birth was closely tied to that process.
With Ho-Oh asleep and entering its rebirth, the time for Marshadow to be replaced was drawing near.
"Doesn't Lord Ho-Oh especially like this Marshadow? Could there be some way..."
Before Ye Lan could finish, Suicune understood what he meant. It silently shook its head, a trace of sorrow entering its calm eyes.
"Marshadow?"
Ye Lan knelt on one knee and gently stroked Marshadow's head as she looked up at him in confusion.
Marshadow tucked her little hands close, afraid Ye Lan had discovered something. But he looked so sad that she began to feel guilty too.
She never should have played that trick on Ye Lan. They were good friends, after all.
Three Poké Balls opened at once, and Serperior, Leafeon, and Rillaboom appeared around Marshadow.
"Hiss..."
Serperior gently rubbed its nose against Marshadow's head, a wistful look in its eyes.
When it first met Marshadow, it had not yet evolved into Serperior. It had never imagined they would be parting so soon.
Nor had it ever sensed such sadness from its usually cheerful Trainer.
Rillaboom said nothing. It gently placed Marshadow on its shoulders and patted her back. That was how Rillaboom expressed its feelings.