Speaking as a human, I have to say that facing off against lizardmen would make me think the following
Holy f@*knuggets dinosaurs/baby dragons, what if the momma is nearby? (Saurus)
What's with the floating frog? AAAAAHHHHHH HE MINDRAPED MY UNIT!! (Slann)
Why are those bushes rustling? Where has the cannon crew gone? (Chamo)
One thing to bear in mind is that noone, especially in the foolish empire, has a freaking clue what's in lustria. Because the saurus eat 99% of intruders. Another .99% find nothing except the most inhospitable jungle on the planet and die of disease. 0.01% find an abandoned city, maybe a few old slann toys and live to tell the tale, but will never in a million years be able to find it again.
So your empire will be coming looking for gold/magic treasures in an abandoned city, they probably had a miserable storm on the way over sinking a couple of ships and making the survivors feel like death would be preferable. They land and there is nothing edible, in fact most of the plants find them edible. Giant bugs, horrendous temperature and humidity, a looming canopy that blocks all attempt at looking ahead and keeps the forest floor in permanent dimness. They are probably lost, maybe following a trail and then... 7 foot high monster lizards surrounded by swarms of chittering dwarf sized lizard things and then WHAT IS GOING ON? Or maybe they stumble across the road to a temple city and they see this hyper realistic statue by the road, a man sized lizard thing wearing a skull helmet, they go up to it and someone reaches out a hand and splat! he's a red smear on the ground (I always liked the TG fluff, makes me think of the guards at buckingham palace)
Anyway, there are a few thoughts for ya