Use two people, use a Rhynoganthia and move it to a safe area. One person tranq it on a griffon if possible or quetz, hop off and ride it when it’s stunned. Second person grab your bird tame while you ride it. Rhynoganthia can move any large enemies or pickup the ossidon if he’s being destroyed. When he’s hurt stand next to a dead body and he will eat it and heal.