My advice is to prepare for Sol as well, because he's stronger than the final boss of the season (by far, IMO). He can wipe your party in 2 turns if you're not prepared with dispels and buffs. But when you beat him, you will hear the BEST SONG EVER!
Seriously, as soon as you beat him, put on some earphones and just listen to the music that comes on during the story sequence. It's an EPIC REMIX of several FF songs, including the main theme, the Exvius battle theme and some other elements from songs like the big bridge thrown in as well. You'll only get to hear it twice (so far), and it's the best song in the game, bar none IMO. I can't get over how awesome that song is.
The other reason you'll want to get on beating Sol is because it will open up the last world in season 1, one of which is roaring volcano which you'll need to get the last raven key. Once you have that (along with ALL the other raven keys), you can start the final raven quest, which will get you the raven's cape. Stick that on Xon (ideally), Lara or your best thief, and you'll get better results (more/better ability crystals) when you do those story events like the one on now.