Nykthos Ramp wants to resolve huge threats off of mana dorks and Nykthos itself, so Abrupt Decay is a premium answer to Elvish Mystic, Llanowar Elves, Old-Growth Troll, and Kiora before they can ramp into Storm the Festival. Hexing Squelcher's Ward protects your board from their removal-light but big-bodied creatures trying to just attack through, and lets your spells resolve uncountered (not that they counter much, but it's a solid rate). Thoughtseize taken proactively is weaker against a deck that just wants to deploy mana dorks and big creatures rather than hold up interaction, so trim it. This matchup is a race, so prioritize killing their dorks early to slow the ramp plan.