This is Critical Strike Damage setup of Hydra which scales very well early. That is thanks to the Invoked Hydra node gaining 50% critical strike damage and 20% crit chance, as well as the Esu's Ferocity Key Passive giving 40% critical strike chance. Hydra gets a lot of Crit Chance for free, where other builds need to invest more!

It also has access to some very good scaling aspects such as Serpentine, Flash Fire, Battle Casters, and Firestarter.You can check this build in detail here