The easiest Digimon to get Kaseidramon with is Veemon. Train Veemon to get Imperialdramon Paladin Mode. Train him to level 95, then do the necessary procedures to Veemon to get Gallantmon. Train Gallantmon's Dark Tolerance to 860 and to level 95. Then, exercise Veemon in the required procedures to obtain BlackWargreymon. Train BlackWarGreymon to level 99. If you have ImperialDramon PM, Gallantmon, and Black WarGreymon at their respective levels, you will get Kaseidramon for Veemon.

Kaseidramon is a Digimon from a Japanese-only Digimon film, appearing as a powerful neutral (not good or evil) Lupin III-esque infamous ronin thief. He is pretty much a Mega-level Flamedramon (but wears none of its armor) in a red Zeon-style uniform with white boots and gloves, with a utility belt around his waist (with a katana and handgun attached to it), with a black desert cape on his body. The front of it is thrown over his shoulder to show his front body, and the back of his desert cape as a yellow falcon sown into it. He has a shield that is similar in appearance to the RX-78-2 Gundam shield. His finisher is "World's Most Wanted" (fires off his handgun, making heavy smoke that materializes to duplicates of him with each of his weapons. One has his katana, the other his Beam Saber, the other his Beam Javelin, and the other his Stride Hammer. They each rush the enemy with their weapon and strike, then using Kaseidramon's infamous thieving skills afterwards to snatch an item).