"This was merely an introduction. Next time, your heads are mine!"
Lancer confirmed with a nod.
Then, with a graceful leap of ten metres or so, he... landed on a shadowy ship that had materialised in the sky. Wood-crafted, it bore no resemblance to modern aircrafts. Likely some form of supernatural arcana. But a familiar sight to the Viking warrior.

"!"
"What's that?" The silver maiden tilted her head in curiosity.
"An underworld ship."
Floating in the sky, the several-metre-large object resembled a miniature Viking funeral ship. Its dragon-shaped keel flowed in a smooth, unique curve. Divine iron round shields lined the hull's sides, and dense magical energy crackled in the air, hot enough to sear skin. Could this be an arcane Noble Phantasm from the Age of Gods?
A large figure, likely the oarsman, stood visible aboard the ship. This unique aura, coupled with the arcane ability to navigate the skies—they were undeniably a Heroic Spirit, a Servant. Their head and upper body were shrouded in a thick hood, concealing their identity completely.
The girl raised her mythril bow, but…
"Huh?"
By the time she tensed to draw the string, the ship had vanished. Gone. Lost sight of entirely. The skyfaring vessel had melted into the shadows, its magical energy and aura dissolving without a trace.

Fate/Lost Einherjar, Chapter 1