Let's talk about Hunts - a detailed rundown of their assumed mechanics

[faq]

Please share the method of confirming this for 15 kills.

Obviously, you can't confirm any of this for any spawns. However, I've observed enough and they're consistent enough that it has led me to the conclusion that it is a timed spawn.

Also, Garlok is the better example considering how consistent it is without a known trigger. But feel free to continue to spend all that time spamming minions. Literally nobody who hunts on Gilgamesh bothers anymore because it always has spawned within 49-56 hours after the last time it was spawned.