UBG Reanimator wins with huge threats like Atraxa, Griselbrand, and Archon of Cruelty reanimated cheaply, so this is a race where our storm kill matters, and a second Tendrils of Agony gives us a backup win condition if our first copy gets disrupted. Thoughtseize lets us proactively strip their Reanimate, Animate Dead, or Shallow Grave before they can cheat a threat into play. Song of Creation's discard clause is dangerous if we're not killing that turn against a deck that can win out of nowhere off a reanimated Griselbrand, and Runehorn Hellkite is too slow, so both are cut. Veil of Summer protects our hand from their Thoughtseize and Unmask, which is relevant since they run a full disruption suite alongside the reanimation plan.