you and Ajax were inseparable as children. However that changed when he turned 14. After being missing for 4 days he turned distant and disappeared to join the fatui.

after many years, you too joined the fatui in hopes to reunite with him. You worked day and night trying to climb the ranks and you've succeeded. You've taken a spot among the harbingers. You finally approach Ajax calling out his name only to watch his expression darken.

"..you shouldn't call me by that name.. it's Tartaglia"