Since the date of creation, the eponymous Solar has always been portrayed by BlackDragonSol in numerous regards, voice acting, storywriting, and design.
Solar was first under concept during around 2009/2010, originally designed as someone who wouldn't die under the circumstance of a proposed death, throughout this it is rather revealed that B-Storyline Solar has been masquerading as his other dimensional counterparts, deceased, or otherwise, in order to gain info on other dimensions and in order to root out threats that could be an exact danger to his interests. Taking their identity, and ore or less stealing it, although with a few notable flaws in which he won't treat whomever is the lover of who he's imitating, as a lover, and any family, not as family. Nonetheless, the impression is usually spot on while he tries to avoid the lover or the family in any other circumstance, especially if who he is imitating is deceased. If questioned on why "he" is still alive, he simply replies that "Rogues never die, they just disappear."
Having no shapeshifting powers of his own, he'd need the help of someone who can cast illusions to carry this trick out, that aside to limiting his actual strength and power, even in some cases showing to be weak, or knowing that taking the place of a live version, especially if they're not aware of the Theory of Quantum Mechanics, causes him to inhibit their body, which may not be so used to the power he holds. Although one thing is normally in common safe for a few things; military involvement. Realizing this string had been taken place, the user of roughly the same name had decided to put him in a paramilitary organization, rather than have him as a full on dimensional trickster fond of stealing identities and imitating people and inhibiting himself within unaware versions.
This military standing eventually evolved to why he is capable of commanding platoons so easily, despite of a young age. It's because he knew how to control larger formations, soon enough, piece by piece, the story of the individual started to be put together and the details were released two to three years later, even having his own elite squad which seems to change members from time to time, although when Black&White more or less transferred into a fan story inspired by the likes of Touhou, and sometimes even taking place within it, but not regarded as Touhou's own canon, the finishing details were put, and since then, have occasionally evolved.