There might only be one Public Event on Mercury for Destiny 2: Curse of Osiris, but there are plenty of goodies to get once you spark its heroic quality. Triggering the Heroic version of the Vex Crossroads public event is actually relatively simple. Here’s how to do it.
Start the event as normal and start killing the Vex until the counter hits 100%.
Once they’re dead, grab the orbs and whack them in the warp gates. The teleports will turn around taking you over to the gatekeepers. Pick a side, blast yourself over there and then take down the Keeper of Ages. Pick up the orb it drop and place it in the warp gate.
Once you’ve done that don’t head back through the teleport. Instead, turn around behind where the Keeper of Ages appears and shoot the Vex Crystal hanging in the air. This will create a platform, from which you’ll be able to shoot more of these Crystals, spawning more platforms until you reach the top of the island where you can activate a plate on the roof.
With the heroic event triggered, a Vex Gate Lord will spawn in the centre are. Kill all the enemies around it and gather the orbs they drop. Dunk these into the gates to drop the Gate Lord’s shield so you can actually damage it. Keep repeating that last process until you defeat it and complete the event for some shiny loot.