Jace, the Living Guildpact

In Commander, Jace, the Living Guildpact is a fringe inclusion — the bounce effect is useful and the looting keeps your hand full, but five mana is steep when you're one of four opponents and planeswalkers die fast at a crowded table. In Legacy and Vintage, the competition from cheaper, more explosive blue threats makes him unplayable competitively. Pioneer is the friendliest non-rotating home: he survives in slower midrange shells where the +1 filters toward your threats and the -3 answers problem permanents. Modern is too fast for a five-mana planeswalker with no immediate board impact. Oathbreaker is the format where Jace, the Living Guildpact most naturally slots in, since his spell-slinging identity pairs well with signature spells that let you cash in the hand-sculpting immediately.