Solar Tablet

An eclipse on demand is a farming tool. The event carries some of the strongest melee drops in the game, and a stack of tablets lets you run it back to back on your own schedule instead of waiting for one to turn up on its own. You have to use it during daylight, and it still ends at the usual evening cutoff no matter how late you started.

Kill the Sun unlocks when an eclipse finishes and never checks whether you killed anything. Wait until the last minutes of the day, use a tablet, then go hide in a hole. The event closes at sunset and the achievement lands anyway.

Temple enemies occasionally wander outside the Temple, and there are ways into the Temple before Plantera, so fragments can pile up long before they are any use. The tablet needs a Hardmode anvil to assemble and will not fire in a world that has not gone Hardmode, so early fragments are storage, not progress.