It looks like there is a database including Thallasium ore for all armor / weapons (Level 1-50) for all weapons and tools, however it looks like the Hammer is not included. Also - there is no Worldgen information for Thallasium, indicating that the ore is not in the game.

I think this is introduced newly by BetterEnd, and probably isn't fully implemented yet

Thallasium is in oreindex - should be fixed