The lightsaber's tale will be told someday. It may be disappointing. It has spurts of use, then long periods of sitting in boxes.
After the beginning of the Clone Wars, this lightsaber was built by Anakin Skywalker, Jedi Knight, and used heavily for about three year in the Clone Wars. At the end of the Clone Wars, for a few days, it was the lightsaber of Darth Vader, Dark Lord of the Sith, and slaughtered a whole lot of Jedi, younglings, and Seperatist leaders. It then fell on Mustafar when Vader loses three limbs to Obi-wan Kenobi.
The lightsaber was taken by Obi-wan Kenobi to sit for near two decades in a box on Tatooine. He may have modified it a bit in that time.
Obi-wan gives it to Luke Skywalker who used it for about three years as he learns about the Force. He than gets his hand cut off by the lightsaber's building (Darth Vader) on Bespin. We lose track of it at this point, only knowing that in three decades it will be in a box under Maz's care. It may have been modified in this time.
It is passed from Maz Kanata to Finn after briefly attracting the interest of its next owner. Finn uses it for a few days at best, striking down a few stormtroopers before getting it pulled form his hand my force on combat. It is then attempted to be picked up by Kylo Ren (nephew of Luke Skywalker and grandson of Anakin Skywalker), but it instead goes to the hand of Rey, who uses it to defeat Kylo Ren (after a bit). Rey than takes the lightsaber back to Luke Skywalker.....