There is a new system called the Ancient Scrolls that starts once you beat the final online boss, Gogmazios (NOTE: this is an urgent so it has to be your quest that you beat, not another players). The Elder gives you Scroll #1 and you are asked to decode it. By hunting enough monsters (appears to be a hidden pt. system so all hunts count toward it, but tough G quests seem to decode them faster), some of the letters will appear. Once all the letters appear you hand the scroll back to the Elder and he unlocks a super hard quest.
‘Super’ Chaos Magala
Dara Amadula Subspecies
Bracchydios Variant (Explosive Bracchy)
Crimson Fatalis Variant (Super Hot)
Multi-monster quest: Frenzied Tigrex, Super Zinoger + Frenzied Bracchydios, Super Chaos Magala, Extreme Selregios (GOD DAYUM)
I am not sure what you get if anything for finishing that final one, but I bet something. So there you have it, the final super quests and monsters are not unlocked via HR like high rank, but a new system that unlocks as you grind monsters. The more you play the more you can play! :p