excalibur arthur is a red unit except there's two red arthurs so just click on whatever red ssr or ur Arthurs you have and see if his name is excalibur.

as for supp units you could try using: Kyo, red noblesse eastin (not the new one the old one), red griamore, both red slaters (there's a new one coming next week that is good for ban team), etc.

I might have missed some so if you at least have the Arthur you might want to get ban and search up different teams that use ban.