Cannot easily say without knowing Cinderace's moveset. Personally guesses Fire, Fighting, and either Poison or Steel moves. Severely doubts another raid for Fairy-types to run wild. Also sort of matters whether you plan to be solo or multiplayer. Cares less about dying in solo. Relies on your Pokemon for all the heavy lifting for the Terastal phase.
Plans to raise a Slowbro for solo raiding, personally. Resists Fire and Fighting. Comes with high health and physical defense (because of Cinderace certainly being physical-oriented). Hesitates to show the build. Hinges on Cinderace's behavior. (Plans to attempt a single, massive Stored Power. Could easily go wrong with a bad buff clear.) May be able to manage with Espathra in solo (not in multiplayer) too. Will see in due time.
Wrote up a few ideas, though.
Armarouge
Tera: Psychic
Ability: Flash Fire
Nature: Modest
EVs: Maximum Hitpoints and Special Attack
Hold Item: Shell Bell
Moves: Expanding Force, Psychic Terrain, Reflect, Acid Spray
Should be good for both solo and multiplayer. Provides great team support with Reflect, Psychic Terrain, and Acid Spray. Deals strong damage as the only Pokemon with Expanding Force, also. Chose a Shell Bell for sustain. Another possibly useful option: Clear Smog.
Ceruledge
Tera: Ghost
Ability: Flash Fire
Nature: Adamant
EVs: Maximum Hitpoints and Attack
Hold Item: Shell Bell
Moves: Bitter Blade, Swords Dance, Reflect, and Brick Break
Completely nullifies Cinderace's two strongest attacks. Mostly relies on Swords Dance and Bitter Blade. Could toss up Reflect for team support. Added Brick Break in case of Court Change giving Cinderace Reflect. May want Clear Smog in the event of Bulk Up or something.
Slowbro
Tera: Psychic
Ability: Likely irrelevant.
Nature: Modest
EVs: Maximum Hitpoints and Special Attack
Hold Item: Shell Bell or maybe Leftovers
Moves: Psychic, Chilling Water, Nasty Plot, Reflect
Suits multiplayer better with the above moves. Drops Attack with Chilling Water, even with the Terestal shield up. Assist more on that front with Reflect. Also hits for decent damage with Psychic.
Other move options: Stored Power, Iron Defense, Psych Up, Slack Off, Psychic Terrain, and Heal Pulse. May want a Bold nature and Defense effort values too.
Pelipper
Tera: Flying
Ability: Drizzle
Nature: Bold or Modest
EVs: Maximum Hitpoints and Special Attack. (Consider Defense instead of Special Attack too.)
Hold Item: Damp Rock or Leftovers
Moves: Hurricane, Chilling Water, Helping Hand, and Roost
Exists more to help out the team than deal damage. Dulls Fire-type attacks with Drizzle. Potentially wastes Cinderace's turns with confusion via Hurricane.
Other options: Rain Dance (especially without Damp Rock).
Credits PKMNcast for some of these. Disagreed on some bits. Largely agreed on the Pokemon to bring, as well as how great stat-lowering attacks are. (Had not considered Pelipper. Forgot about Expanding Force as well.) Bets on some Pokemon like Skeledirge working okay too.