Basically be a slut for them, so keep submitting to the Lizardmen, including the friendly ones..
there is a scene at the waterfall where you 'help' out 2 warriors, during the contest you can spitroasted by roth and a warrior, you can submit to the warriors at the ruins indeed, but also submit to rhot and then suck his dick, ehmm.. and do horny things with Xer.
There were also lewd scenes only during the stories that only happens once so they are unfortunately not repeatable (like getting spitroasted by 2 warriors, ganged up by a whole group..)