One of the biggest changes that arrives with the update is the addition of an Assassin-specific weapon, the Duskblade of Draktharr. “By clearly calling out ‘Hey, this one’s for you!’ we can start to set an expectation around how an assassin can act in fights, as well as the kinds of power-curves they should have long-term,” Riot Games said.
Patch 6.3 tweaks Dragons’ stacking effects, fixes Alistar’s headbutt skill, nerfs several champions (Corki, Poppy, Graves, and Ryze), and buffs a couple of characters (Ziggs and Xin Zhao). Players will also no longer be able to see enemy champion picks before matches.
Source: Patch notes