Personnally i would like a area similar to areas 9 to 11 from the jurassic frontier as our "nocternal" map, the rotten vale is our cave area and i think necrylla would fit perfectly in the vale. but back to the "Fungal Wastes" as i call this hypothetical area, the food chain would go like this using monsters we already have and adding in small monsters (from top to bottom) Nargacuga > Garuga > Malfestio / Nescylla > Kut-ku > Konchu. with Chamelos as this area's elder dragon and duramboros doing whatever he wants. Narga as Apex beacause he is the perfect ambush preadator, then into Garuga beacause i couldn't think of anything else. Malfestio and Nescylla are equals beacause they both have sleep and are fought as the HR 4 urgent quest for their respective games. Kut-ku, do i even need explaining, and Konchu, beacause both the vale and the coral highlands don't have herbivores, so Konchu are okay in this hypothetical ecosystem.