The game never shows a drop percentage. Rarity here means access: about an hour of upgrades before the first summit, and only two or three climbs per stamina fill.
Golden rare demon egg. After roughly an hour, a player grabbed an egg they called a rare demon egg and said it was golden. It may be the rare label plus a golden look, not a unique species. No hatch was recorded. A guess of over 12 hours was the player's estimate, not a shown timer.
Eternal eggs above Special. One player called Eternal the final stage at that moment and said those pets let them return for the eggs. They also asked whether Eternal beat Radiant and never settled it. Radiant, Vassal, and Royal share that upper zone.
A long timer is a hint, not odds: rainbow ocean 20 minutes, a very high egg 2 hours, dinosaur-area 6 hours, divine rainbow 8 hours, tough eggs 11–12 hours or 778 minutes.
Mythic T-Rex
A full climbing session checked for this claim never showed the word Mythic or a T-Rex. Labels that did appear were uncommon, wooden, common, rare, epic, legend, divine, Radiant, Special, and Eternal.
What is real: a dinosaur area, dinosaur eggs that are not always present, a sparkle on a rare egg and on a dinosaur egg that vanished at the grab, and hatched dinosaurs at about 450 million and 800 million. Text sometimes moved too fast to read, so one session cannot prove an egg is absent. It also cannot verify a Mythic T-Rex route.
Rare is not best. A 12-hour egg can lose to a shorter one. Compare goals on best eggs.