Its an Always Watching on a body, and its almost always available as a lower-power creature to trigger coven
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It's no surprise, then, that all but one of them were killed by the dragon Planeswalker Nicol Bolas and his ancient, forgotten Amonkhet gods: the Scarab God, the Scorpion God, and the best of the bunch, the Locust God
(For a deeper look at some of the best decks of that time period, Randy Buehler took a look with his article "Throwback Standard Gauntlet 7: Worldwake ".) While we didn't end up hitting the card where Standard would have wanted it to be for the best Standard environment long term, Jace certainly became even more iconic after Jace, the Mind Sculptor was introduced and has proven to be a format staple for many of our older formats
Every turn cycle, you generate additional value in the Undercity without having to invest any resources of your own