Early in the game, it forces opponents to pay extra mana or lose their key creature or planeswalker
Casting Emrakul, the Promised End on six mana is obviously insanely good, but very difficult to set up
Eiganjo Castle Most white commanders could justify Eiganjo Castle given that they always have at least one target, and a mild protection spell that slots into the land base is pretty decent value
Ripples of Undeath is the kind of self-mill Ive been waiting for
However, some cards are designed to punish the opponent for attacking recklessly, and Orthworm ex is one of the most intriguing options in this regard
Engle Mythic Forestwalk (This creature can't be blocked as long as defending player controls a Forest.) If one or more tokens would be created under your control, those tokens plus that many 1/1 green Squirrel creature tokens are created instead