To those that wanna find this demon you’d better go to the mountains. The volcano, fars peak, whitesky peak or any other high peaks out there. They are as rare as a Quetzal probably according to the wiki. If you wanna see one mount a high level Pteranodon with a good enough saddle and high health(mine was a lvl 140+ when my cousin dared me to shoot him in the head). You’d better use a spyglass or risk falling without a parachute into the giga’s mouth. If it notices you don’t go straight to your base it’ll massacre it and all your tames. You’d better lead it to the gulch of lamentation or a place full of other carnivores to distract it then safely get back to your base.
If one is encountered near water, you can simply lure it out to sea with a flyer and it will swiftly drown. Given the water is deep enough. If encountered inland not near water. Pray to the overseers you have something fast enough to out run it. Then promptly die because they're as fast as a mad Hispanic mother with a shoe. Not as deadly as one though.