mtg play test cards Zyym, Mesmeric Lord [Mystery Booster Playtest Cards] Whenever an opponent pays a tax from a spell or permanent you control Do-Over [Mystery Booster Playtest Cards]

This is a solid effect in some decks, but so far its been a niche piece in the grander scheme of Magic

For two mana we get to look at two cards, which is a great rate

Cards like Mental Modulation will help to keep the spell count flowing

You often find yourself playing against other control decks that have random one- and two-power creatures that look to nickel and dime you while you build up your mana

You can also win by milling your opponents deck so they are unable to draw a card on their turn, which is a goal for Dimir, or you can hit a certain life total that triggers victory due to a card abilitylike Angel of Destiny, which is featured in white decks

If they are holding removal or countermagic you can take that away, see what other options they have and then do your own thing with perfect information and safety