rare dragon ball heroes cards What are the Most Valuable Cards? UGM2-SEC3 Cell (2022)

Defensively, Book was just a great answer to blocking attacks

For example, if My Tendrils Run Deep is in your command zone face up and you control Exploration (an enchantment with "You may play an additional land on each of your turns."), you'll be able to play three lands during each of your turns

Selvala, Heart of the Wilds The most important resources in Magic are mana and cards, so any card that gives you an advantage in both regards becomes quite strong

You could give them genuinely useful things, double-sided effects which work the same regardless of who controls them, or any number of actively detrimental effects