First, in your combat phase, you turn a land into an Elemental X dork with trample and haste equal to this guy's power, so minimum 3/3
You might choose a commander who interacts uniquely with lands, like Soul of Windgrace, or Titania, Protector of Argoth
You can also find more details about your favorite TCG in our guide to the MTG release schedule.
Summoners Grimoire is a bit less exciting, but its still a nice way to cheat out big Summons
Its also nice to have a 0-mana sacrifice outlet attached to a commander, though this one isnt nearly as powerful as the likes of Yawgmoth, Thran Physician
The only black based decks which dont play Thoughtseize at all in Modern are highly synergistic decks like Goblins or Mill, or decks which cant afford to play it due to other restrictions like Living End