They give you an immediate bonus when played (like using your Planeswalkers ability immediately), but instead of needing to protect them, you give them to your opponent (its useless for them)
Brawl Not Legal Vintage Legal Timeless Not Legal Commander Legal Pauper Not Legal Oathbreaker Legal Penny Not Legal Toolbox Buy This Card Notes and Rules Information for Second Guess: Second Guess cant be cast unless the spell it targets is the second spell cast this turn
I really like Valki as a multi use card which can be used to hit a card from each opponent's hand, or a late game powerful Planeswalker
Interestingly, this deck contains a built in three-card infinite combo that is relatively easy to pull off if you can find the requisite cards
The Gitrog Monster, Slogurk, the Overslime, and Titania, Protector of Argoth will especially benefit from Constant Mists