Inviolability

Inviolability sees essentially zero play in Legacy and Vintage, where creature-based strategies fold to faster, more brutal disruption before a two-mana aura does anything relevant. Pauper is the outlier — at common, Inviolability occasionally shows up in Aura-based white aggro as a cheap way to protect a key attacker — but it's fringe there too. Commander is where it genuinely earns a slot: the multiplayer threat density, longer games, and prevalence of combat make protection from creatures a meaningful deterrent, and the Pariah combo that requires Inviolability is only viable in a format where you have turns to set it up.