Cast bears, then grow a bear or set up a fight
Its still used that way in Premodern, Vintage, and Legacy, adding spice like Kalastria Healer or Spike Feeder of all things in some builds, and looking to infinitely bounce your creatures for Grapeshot in others
On a bad roll, the least it could do is copy of a target creature you control (tapped and attacking)
With double the triggers, you can not only initially untap the land, but then also tap it in response to the second untap trigger, netting you two mana off of your tapped land the turn it enters the battlefield
What competitive formats is Sorin, Imperious Bloodlord played in
The estimates below are derived from multiple documented OP15 box and case openings including a full 12-box English case, a single Japanese box, and a comparison opening of 24 blisters against a booster box