While this is an effect that can more reasonably be tracked with paper cards, it becomes substantially simpler in a digital space
(Choose any number of permanents and/or players, then give each another counter of each kind already there.) Illustrated by Dave Kendall Standard Not Legal Alchemy Not Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
It helps you find more fuel and punishment while raining damage on your opponents
This can be replaced with another value land like Emergence Zone
Over the years, Wizards has toyed with many different flavors of Sagas--variable number of chapters, all kinds of effects, creatures that transform into Sagas, Sagas that transform into creatures (especially in Kamigawa: Neon Dynasty) , and even an Enchantment Land that's also a Saga
Notably, it doesn't need to be the same legendary Assassin you controlled when the ability initially triggered