In Mark Yetter's patch preview, Aphelios, Aurelion Sol, Kassadin and Mordekaiser were listed as the champions set for a nerf in patch 10.1 while many more are expected to see buffs and support item changes will also be dropping ahead of the new season.
It's so good to be back! 10.1 Patch preview, let's get this season started right! pic.twitter.com/XGtcLiSxi2â€” Mark Yetter (@MarkYetter) January 6, 2020
Newest champion on the Rift (for now) Aphelios will see an Ultimate nerf for the Infernum flamethrower weapon. Moonlight Vigil will see the multi-hit AoE deal 75% damage. His movement speed will also be dropped from 330 to 325 and his base HP dropped from 530 to 500.
Aurelion Sol will see his Passive deal 12-120 damage rather than 16-120 and Kassadin will see a small movement speed nerf from 340 to 335.
Mordekaiser has been a dominant force in the preseason so far and Riot's nerfs will see his Passive duration dropped to four seconds and movement speed changed to a flat 3%.
It is not all nerfs in this patch, with 12 champions in total seeing varying buffs to their abilities, health, etc.
Azir and Corki are seeing damage increases for their respective Ultimate abilities while Jax's R Passive will now work correctly with Guinsoo's Rageblade and Vi will stay unstoppable during her R knockup animation.
Jayce and Varus will see Q changes, with damage increases for the Defender of Tomorrow and cooldown reduction and blight refund drops for the Arrow of Retribution.
Nami and Zyra get E buffs alongside Sejuani, who also sees Increased Passive resistance and HP per level, a buff shared with Kalista.
Shyvana will gain a Passive stack when the Elder Dragon is slain while Cloud Drake will increase her Fury gain. She will also gain E on hit damage, rising to 3.75% max HP from 3.25%.
Sylas sees the most dramatic buffs that change every aspect of his kit from his base stats to his R Ultimate. With so many changes, this will be covered in a full article once the 10.1 patch drops. For now, the preview notes have a full page of the expected differences.
The 10.1 patch and its accompanying notes are expected to drop on 8th January with the full details.