Prydwen

Prydwen is a treasure owned by King Arthur, said to be a "wonder tool" able to become both a ship and a shield. Having stored it in Camelot's treasury, Mordred stole it from Artoria during her temporary rule while Artoria was away.

Prydwen Tube Riding
Prydwen Tube Riding： Kingly Mood of Reining in Surging Waves! is a technique used by Mordred after having her class container modified by Scáthach. Bringing forth Prydwen and modifying it into a surfboard because she was looking for a "surf board that could withstand her power", she rams the opponent head-first with Prydwen while, a surfing technique where she runs through the gap of the waves. Said to boast a "top-class degree of difficulty among the surfing techniques", she "feels exactly like a king that rules the sea" while performing the technique.