First of all Hecarim, who is to blame for the delay on the patch. Apparently he broke things, hard.
Hecarim: The Shadow of War
Abilities: information pulled from the PBE, numbers are subject to change on release. Warpath(passive): Hecarim ignores unit collision and gains a small attack damage increase based on his movement speed. Rampage(Q): 25/25/25/25/25 (may be a bug on the PBE) Hecarim cleaves nearby enemies dealing physical damage. Spirit of Dread (W) 50/60/70/80/90 Hecarim deals magic damage in a radius over time. Hecarim gains a percentage of life back from ANY damage done to enemies in the radius. Devastating Charge (E) 60/60/60/60/60 (also bug?) Hecarim gains an increase in movement speed, his next attack knocks the enemy back and deals additional damage based on the distance he traveled while the ability was activated. Onslaught of Shadows(R) 100/100/100 Hecarim summons spectral riders and charges forward, dealing magic damage in a line. Hecarim creates a shockwave when he finishes his share, dealing additional magic damage to nearby enemies causing them to flee in terror.
Blood Knight Hecarim
This patch preview goes over the major changes, most importantly, TEEMO BUFFS!
Varus has also shown up in the PBE but only in the champion list, not available to try yet, and no info other than his abilities.