He may look like a human, but his body create by "The Hooded Man" with prototype, GEAR project and bioweapon to create "The Ultimate Being" which can't be specific explain. His real name is Daniel, the assistant who work for The Hooded Man until the incident that most of the top students betrayal him and steal his project (Which is impossible to access). So he put an experiment on Daniel, and gave him a code name.
SOL vow to get hooded man and continue his journey to defeat the top students (who know the immortality and infinite) to claim his revenge...despite he's a cold but he has a good heart to respect his comrade.