Eldrazi's Chalice of the Void set at zero or one can lock out our Brainstorm, Ponder, and Narcomoeba-based combo, so Fragmentize destroys it outright (it costs 0 or more, qualifying under Fragmentize's mana value 4 or less restriction) while Pithing Needle can name Chalice of the Void to stop it from entering with relevant counters or shut down another key activated ability. Cabal Therapy and Dread Return are weaker here since their deck has few creatures worth sacrificing for and reanimating Thassa's Oracle is less reliable against a deck that doesn't interact with our graveyard. This is a race against their Ancient Tomb-fueled hand disruption and big threats, so prioritize resolving our engine before Chalice locks us out.