When you've beaten it down for awhile (I've never actually killed one) it disappears and lots of
Stone Mutant Waragon and Stone Waragon spawn. When you've almost killed then all a red circle appears on the ground and then Colossal Stone Waragon comes back at full (?) health for the next round. Rinse and repeat. Might have better luck with higher level and better gear.
Its Def killable just get full Pen Tuvala (aka Season Gear) and it's sufficient. dodge the red circles and kill the mobs it spawns near the end of it's health it will start spewing poison at you. I think it was meant to emulate a mini boss. The minimum AP DP for the area are 150 220 BUT since it shows, when you click the Mob Icon for Waragon Nest and it has that #Party of 3 it means the mobs have enough health to require equal damage from 3 people to kill it at the same rate as a normal mob within that range. so that's why I said pen tuvala cos that puts you at ~245 AP 300 DP. and it's good enough to solo
Also be at least minimum level REQ for area because other wise monsters gain like 90% more damage done on you and receiving 90% less from you aka Purple Named Mobs
Hope this didn't confuse you more
Basically Monster Zones Designated: #(x)Party may have an appropriate looking AP/DP req and Level but the mobs have exorbitantly more health by design for party play