Emerging Conduits. They were Triglavian Invasion combat anomalies that would spawn outside of invasion systems. Used to be that they had a 1 minute respawn timer and would drop more red loot (stuff that could be sold to NPC buy orders -kind of like blue loot from wormholes, or overseer effects from exploration sites). So, not only did they drop more loot, but their spawn rate meant you could sit in one system, which decreased your travel time.
CCP ended up reducing loot and increasing the respawn timer so that you had to fly around. But they were ubiquitous enough that you could just continously loop through 3 or 4 systems and still make respectable money. It was no longer the best, but it was easy, low risk, and could be done while watching youtube or whatnot.
Unfortunately, they may have been nerfed again. They seem to have disappeared from non-invasion space, and M Cincinnatus says that they’re now harder and payout even less.
Looks like it’s time to pivot again.