He should be out next month. There is a more info under the tier list section if you want to check out his abilities. Keep in mind you will need 30k visiore to max him out. We should be getting some shards from hard quest and visiore spending so it may be less. Hopefully we get a free 10x pull so you can reroll till you get him and spend the remaining visiore on his shards.
Thanks for clarifying this. I was gonna pass on trying to get +5 because the grind would've been insane (clearing the tower multiple times). If I pull Rain I will definitely use him and get the weapon to 5 stars.
So the Crimson Saber only comes in one form because you can only get one of them (at least so far) - it's a reward from the Tower, and to get it to +5 it is actually unique and requires upgrade materials from re-clearing about 2/3 of the Tower.
It is primarily a weapon itemized for Rain's use, that's why it has so much MAG on it, it's probably not good for any of the other greatsword users really