Mono Red Rally wants to flood the board with cheap creatures and close the game with a Goblin Bushwhacker pump or Rally at the Hornburg token swing, so your priority is surviving the first few turns and stabilizing with blockers. Prismatic Strands is your most important card — hold up mana and flash it in response to their all-in attack to negate their best turn entirely. Suffocating Fumes at instant speed wipes their 1- and 2-power creatures; bringing in the second copy gives you more chances to clear their board before they reach lethal damage. The additional Tithing Blades drain life on entry, which directly offsets the reach provided by Lightning Bolt and Chain Lightning in the mid-game. Trim Omen of the Dead and Grim Bauble, which are too slow to meaningfully impact the race, and shave a Thraben Charm since your suite of Cast Downs and Fumes already answers most of their threats.