Narrative Freshness: Using a brand-new entity like Titan X allows writers to craft a fresh mystery without being restricted by the established backstory of Amhuluk found in the Godzilla Dominion comics.
Scale and Threat Level: Official descriptions position Titan X as a "god-like" force larger than both Godzilla and Kong. In contrast, Amhuluk is a subordinate Titan who famously submitted to Godzilla, making him less suitable for a season-long "ultimate antagonist" role.
A Clean Slate for Mystery: Since lore experts already know Amhuluk resides at Outpost 66 in Russia, introducing a new Titan creates more suspense regarding its origin and the "top-secret" nature of the 1984 Soviet mission.
Environmental Design: Titan X is an aquatic, bioluminescent, tentacled monster designed for deep-sea and coastal action. Amhuluk is a plant-based creature made of forest debris, which may not have fit the specific visual themes the showrunners wanted for Monarch: Legacy of Monsters Season 2.
Expansion of the Pantheon: By creating a new Titan, Legendary expands its "stable" of original creatures rather than relying on existing comic characters, giving them more long-term freedom for future films and series.
Even though both monsters share a Russian connection, the shift to Titan X allows the show to deliver a bigger, more unpredictable threat for the live-action screen.