Valve just rolled out the "Dueling Fates" update today for Dota 2, bringing the game up to version 7.07. This update adds in two new heroes: Dark Willow and Pangolier. It also includes a literal metric ton of balance changes, fixes, gameplay mechanic changes, and more.

Valve's special "Dueling Fates" page is about 90% changelog, so you're just going to have to go there to check it out for yourself. Trying to paste it here and have it be formatted somewhat properly would be an absolute nightmare that I just don't have the will to tackle right now.
Today the Dueling Fates collide, as join the battle of the Ancients.
And neither arrives to the fight empty-handed. Each hero has a debut Immortal item available in the Emblems of the Dueling Fates bundle, which also contains a Ward set, courier, and taunts for both heroes.

Along with the new heroes, Dueling Fates also introduces the 7.07 Gameplay Update; new ranked seasons for MMR; an entirely new game mode; and more. Visit the update page

Seriously, it's a huge update.