Arna's attack trigger essentially enables attacking Living Weapon creatures to split off and make their controller's board wider, or go-tall with stackable effects like Drossclaw's draining attack trigger or Nettlecyst's massive boost based on artifacts and enchantments
Here are the cards that are now unbanned for legal play, as of December 2024: The reasons for the decision to unban these cards are elaborated on in the official Wizards of the Coast announcement, where it is explained that "the whole point of today's reversed bans is to call back to the Modern of yesteryear." With Magic: The Gathering constantly introduces new cards, where older ban decisions may become no longer relevant
0-1 Land cards
Yawgmoths Bargain First Printed: 1999-JUN Banned: 2006-MAY Yawgmoths Bargain abuses Commanders higher life totals, making the life payment essentially trivial
Mardu attack triggers make Isshin, Two Heavens as One a superb support piece
I won't go deep into this topic here because this is a deck tech not a format philosophy piece, but suffice to say I think it's Mono Red, especially when you're on a budget and don't have access to the top handful of staples like Dockside Extortionist, Underworld Breach, and Jeska's Will
