mtg card abilities list Top 20 Ability Support Cards in Magic: The Gathering MTG Cheat Sheet Evergreen Keywords

If an effect allows an opponent to cast spells any time they could cast an instant (for example, if your opponent also controls Teferi), the restriction of Teferi's last ability takes precedence over that permission

If a creature targeted by the "turned face up" ability dies before that ability resolves, it will become an illegal target even though it may be a creature card in a graveyard when the ability resolves

That said, some items can break the rule

Most major set releases also come with Commander decks, and with so many sets a year, there are a lot of Commander decks being released constantly

Your biggest problem will be defending Teval, who has no protection against removal, will suffer when cards are exiled, and who must constantly jump into the fray of battle