Bring around 6-7 or more rexs and when it lands everyone get around it and trap it. Deathworms will come and knock u back but just keep moving forward slowly so u dont get pushed out. Even when the rock golems come don't stop hitting it. Goodluck boys :)
When fighting the manticore a good strategy is bring in high level Rex's with good saddles and circle the manticore it then becomes pinned allowing you to kill it without it flying all around .... watch out for the poison it shoots at you though it will kill you off your mount like the poison wyvern ..
Easy boss, bring 5-6 decent Rex's surround the boss when it land preventing it from flying high. Once it try's to fly it will be stuck and you can kill it easy, have one or two people on Rex's walk around and kill death worms and remember where the bags drop. Once the rock elements come out the two not attacking the boss go back and kill the boss once you defeat the boss go to the death worm bags collect the black pearls. EASIEST BOSS.