yugioh premium pack 1 booster box Yu-Gi-Oh! Unboxing selected by the Yu Premium Pack (Japanese) - Yugipedia

By focusing on this attacker-support system youll have a more cohesive deck that executes its strategy smoothly

Criteria: Nonland cards that care about the number of Swamps either you or other players control, or that otherwise trigger when a Swamp is tapped or enters the battlefield

These were first introduced in the Black & White era, and have been teased to return in Wild Force and Cyber Judge

You get seven of them (eight if you played Miirym) meaning a massive buff for your whole board, and a ton more Terror triggers

Well know soon enough

Well, as I said, its a supply-side issue that led to the inflated price of Caverns, rather than a demand-driven problem