User blog comment:Spartan-091/ProTips: How to Circumvent Our NCF Policy (Apologies to Ajax for the Method)/@comment-131756-20100929215552/@comment-4791767-20100930184521

Other than the obvious (Precursors predating the Forerunners), Forerunner are Tier 1, which means they're pretty advanced but they do have some plausibility in their science. The Precursors however, according to the Forerunner Technological Achievement Tiers have hit the theoretical ceiling of Tier 0. I'm guessing by what the Halo Encyclopedia describes as transsentience, could be something akin to the Ascended Ancients in the Stargate franchise.