As a Skíðblaðnir, Ryuuteimaru will grow and evolve into different forms by using the aura and imagination of its master as its source.
It has even been stated that Ryuuteimaru could potentially evolve into its own dimensional plane.
Of course, we could always wait a few months for the light novels to see how it turns out.
However, as an impatient person, I say: F*** That!
Why don't we let the fans come up with what it will look like to pass the time?
Here are my ideas:
- Ryuuteimaru as a floating harem palace: I picture a massive, crimson colored, floating ship adorned with statues (since this is Issei we're talking about, I'm sure you can tell what of).
- Inside of the ship is
- A large number of bedrooms, each with their own unique style.
- A massive living room with a huge flat-screen TV.
- A study (filled with Issei's "collection")
- A storeroom
- A movie theater
- Training rooms
- Changing rooms (with a small hole in the wall for Issei)
- A large indoor bath with a refrigerator filled with 3 flavors of milk (fruit, regular, and coffee)
- A heated indoor swimming pool
- A dungeon
- Ryuuteimaru as a dimensional plane: I'm thinking of a world about the size of the Earth and the Underworld. In this world, all the normal animals are replaced with their monster girl (ex. harpy's for birds) counterparts. There is a mansion (or maybe a castle) somewhere in the world where Issei and his harem and peerage will reside. I need not say anymore.