Proposed Theros update
Sign in Blood -> Read the Bones is nearly a strict upgrade.
Tendrils of Corruption -> Erebos is mostly because Erebos seems interesting.
Brainstorm -> Thassa is to up the creature count, and I like upkeep: scry 1
Spelltwine -> Curse of the Swine is partially flavor, partially that Pongify wasn't represented, and I really like this version.
Engineered Explosives -> Ring of Three Wishes is flavor / interest in the Ring.
Cloudthresher -> Arbor Colossus is partially a desire for Monstrous, partially that the player-damage component of Hurricane effects isn't particularly Green.
Thornling -> Nylea is a result of Nylea's abilities being very Green and Thornling's not.
Wood Elves -> Sylvan Caryatid is intended to help greedy multicolor decks, and avoid the name issue.
Vithian Renegades -> Xenagos: The Renegades are solid, but I think multicolor cards should *feel* multicolor.
Cone of Flame -> Hammer of Purphoros: Hammer's neat, Cone is underperforming.
Fireball -> Purphoros: The God is a total house, Fireball is a concept better executed by Comet Storm
Demonfire -> Stormbreath Dragon: I want more great creatures in Red, Demonfire is the most lackluster of the remaining X spells.
Act of Aggression -> Zealous Conscripts: I don't really like the Phyrexian mana here, as it means that one of the better Red cards can be used by any deck. The ability is also not generally supposed to happen at instant speed for Red, and the Conscripts can steal any permanent for hilarious interactions.
Windborn Muse -> Helios: Helios seems interesting, the Muse is a bit underpowered now.
White Sun's Zenith -> Elspeth, Sun's Champion: It's sad to break apart the Zenith cycle, but the newest Elspeth is just clearly a better card.