The 10 illegal cards are extremely powerful and would definitely warp Historics meta
Ankle Biter Caustic Bronco Constrictor Sage Enduring Tenacity Fangkeeper's Familiar Jade-Cast Sentinel Lasyd Prowler Mold Adder Naga Fleshcrafter Rottenmouth Viper Scalding Viper Scathing Shadelock Serpent Specialist Sidisi, Regent of the Mire Skyserpent Seeker Soulcoil Viper South Wind Avatar Sultai Devotee The Serpent Society Vizier of the Menagerie
Syr Armont, the Redeemer Selesnya enchantment decks can be very strong, and if you want to have an anthem on hand at all times in one of these enchantment decks Syr Armont, the Redeemer gives you the option
This can target any targetable creature, also, unlike spells like Go For The Throat which I see played a lot in EDH
With reanimation spells and a sacrifice outlet, you can also take more control of the ramp and land tutoring, keeping you on pace with the greediest ramp players