Why Dark Elixir is the game's rarest resource
Dark Elixir is deliberately scarce. It only appears from Town Hall 7 onward, it has its own dedicated storage, and its passive income — the Dark Elixir Drills — trickles in far more slowly than gold or elixir collectors. Most of your Dark Elixir has to be raided, and enemy Dark Elixir storages rarely hold much, so a single big upgrade can mean dozens of targeted attacks hunting for it. That scarcity is exactly why players outsource it: it is the slowest resource to accumulate by hand.