Golgari Midrange is full of discard and targeted removal (Duress, Bitter Triumph, Assassin's Trophy), so Defend the Rider protects our key threat. Soul-Guide Lantern denies graveyard-based recursion and gives us a later card draw. Spell Pierce is weak since Golgari plays a grindy, mana-abundant game by the time key spells land, so it and the clunky Terrian, World Tyrant plus a Lumbering Worldwagon come out for more protected, resilient threats that dodge their removal-heavy plan.