When did necrons come out?

Necrons were first introduced in the Warhammer 40,000 universe in 1993 as part of the game's third edition. They were featured in the "Warhammer 40,000: Rogue Trader" rulebook and later received a more detailed codex in 1998. Over the years, they have undergone various updates and redesigns, with a significant revamp occurring in the 5th edition in 2011.