This theft triggers an unprecedented crisis. The Mage’s Association, desperate to reclaim the Grail but lacking the resources to launch a full-scale assault, employs a scorched-earth policy: they use their "Red" jewels to summon seven Servants to form the Red Faction. In response, Darnic Prestone Yggdmillennia uses his clan’s reserves to summon the Black Faction. Thus, the Great Holy Grail War begins—a massive battle royale consisting of fourteen Servants, divided into two opposing armies.
Both Atalanta (wishing to save all children) and Amakusa Shirou Tokisada (the secret mastermind behind the Red Faction) seek "pure" salvation. Amakusa wishes to use the Greater Grail to grant immortality to all humanity, eliminating death. The heroes argue that mortality is what gives human effort value. By removing struggle, you remove humanity. Fate Apocrypha
While the first half is a fast-paced war, the second half is often seen as "clunky" or a "sludge fest" of exposition before the final climax. This theft triggers an unprecedented crisis