Guilds of Ravnica Niv Mizzet, Parun , Emmara, Soul of the Accord , Lazav, the Multifarious (decklist in the comments) , Tajic, Legions Edge , Etrata, the Silencer Commander 2018 Aminatou, the Fateshifter , Xantcha, Sleeper Agent , Lord Windgrace Core Set 2019 Sai, Master Thopterist , Goreclaw, Terror of Qal Sisma , Vaevictis Asmadi, the Dire , Chromium, the Mutable Battlebond Dominaria Teshar, Ancestors Apostle , Grand Warlord Radha , Arvad the Cursed, Muldrotha, the Grave Tide , Slimefoot, the Stowaway , Yargle, Glutton of Urborg , Squee, the Immortal , Firesong and Sunspeaker , Jodah, Archmage Eternal Masters 25 Rivals of Ixalan Azor, the Lawbringer , Etali, Primal Storm , Nezahal, Primal Tide , Zacama, Primal Calamity , Tetzimoc, Primal Death , Zetalpa, Primal Dawn , Ghalta, Primal Hunger Unstable Grusilda, Monster Masher , Dr

Utility, Sideboard, and Flex Options The above group of cards expands beyond the five shown, but these are the most important options available in terms of tuning Mono-Red Prison to an expected metagame (this is partially a farce due to how wide-open Legacy typically is, but you can still take a general guess at what the winners metagame will be)
Avatar Aang will be great in that very narrow archetype and useless outside of it
Its Ability of Tandem Unit allows the player to place two Basic Electric-type Pokmon from the deck and put them on the Bench
This is the game for them
Aeve brings an oozy army to the table, and with plenty of ramp and card draw, youll never run out of slimy reinforcements