Would be cool if the OP actually explained when/where any of this happens.
Perhaps you haven't spent much time in-game. Invasion events (like Nemesis and Rikti invasions, when active) occur pretty constantly in random zones, and their starts and stops with locations are always announced in your chat box with a taunt from the enemy character.
Mapserver Madness! (Four-One 2022 Invasion Event)
in Events & Contests
Posted
Perhaps you haven't spent much time in-game. Invasion events (like Nemesis and Rikti invasions, when active) occur pretty constantly in random zones, and their starts and stops with locations are always announced in your chat box with a taunt from the enemy character.