The Throne costs 4 to cast and 3 to equip. The Equipped creature has defender and “2, tap, Other creatures you control gain trample and get +X/+X until end of turn, where X is this creature’s power.”
It’s obviously not a cheap effect to use. But on the right creature, you could make other people’s lives quite miserable. One Magic player on reddit once suggested that Zurgo Helmsmasher and his base 7 power could become a fantastic target for this card. He would then be given defender and wouldn’t have to attack every turn, either. Giving all of your creatures +7/+7 and trample seems pretty legitimate for a tap ability that only costs 2 colorless mana. While Zurgo has become a popular Commander, the Throne hasn’t really been a huge hit with him.
The question is, where did Dragon Throne of Tarkir end up being played? Most of the time, it takes at least 7 mana to get this cast and equipped to a creature. Yes, it could be a mighty finisher. It’s much too slow for most Constructed formats. It was a Limited bomb on any creature that has any significant amount of power. Plus, you can boost the power of the equipped creature before using this effect. But even as an Equipment with a lot of potential in Commander, it’s still proven a bit clunky.
Still, there are plenty of Commanders that never feel the need to attack, but have high enough base power to make the Throne’s effect worth it. There are those more than willing to gain Defender in order to help their minions deal massive amounts of damage. Honestly, any equipment-based Commander deck can enjoy this card. My favorite Commander for this card is Kemba, Kha Regent. I imagine her on the throne saying: Go my kitties! Attack with great ferocity! I’ll just sit here with all my shiny toys on my pretty new throne!
Unfortunately, most aggro builds don’t like the idea of losing their Commander to becoming a defender. Such decks usually have other creatures with high enough power that can serve as the Commander’s “regent” while the Commander leads his/her/its forces into a decisive strike against the enemy. Outside of Kemba, the only other Commander to adopt the Throne is Lovisa Coldeyes. This does make some sense. Lovisa pumps all Warriors, Barbarians, and Berserkers by +2/+2 and gives them haste. Her deck has only improved over the years with Warriors and Berserkers still being printed on a regular basis. Lovisa really doesn’t mind sitting on the throne. It fits her flavor anyway.
The Dragon Throne of Tarkir was clearly designed to be a Limited bomb and casual favorite. Game of Thrones jokes aside, there will probably be other Commanders in the future that could prove to be a good fit for this Equipment. If you play Kemba or Lovisa, this card comes highly recommended.