So, I was unfortunate enough to find the horrors behind the Xeric Shrubland, a biome added from the Biomes o' Plenty mod. Turns out, the Xeric Shrubland is home to cockatrices, deathworms, myrmex (desert variant), and LOTS of all of them. I haven't explored the entirety of the Xeric Shrubland I have found, but in less than half of the biome, I've counted somewhere between 12 to 14 cockatrices, 5 to 10 deathworms (I was more focused on counting the cockatrices-), and two myrmex colonies (one was MASSIVE, with 3 entrances). Although this biome does also spawn desert temples, I don't see any worth in risking this biome, unless 1, you're already kitted out with powerful gear and/or strong pets, or 2, you're a masochist and enjoy suffering. ¯\_(ツ)_/¯
For those who are willing to take on the challenge of the Xeric Shrubland, I suppose you might need a few tips if you don't know what you're doing...
There's two ways to deal with the cockatrices (actually there's three, but we'll just combine two and call it one way). The first method is to tame the cockatrices. Of course, this is the time-consuming route, since cockatrices are difficult to break. But if you're looking for a loyal warrior/pet, then a cockatrice is a good fit. When encountering a cockatrice, keep your distance - it'll give you time to fall back when you're health gets too low. When you get too close, tower up or swim across a river if one is provided (they are slow swimmers!). Make sure you bring a lot of food to keep your hunger and health up. Stare down the cockatrice, taking breaks to heal, until it finally gives up and ignores your presence (that's a good sign that you tamed it). Then you can tell it to do as you please! The second method of dealing with cockatrices is simply killing them. Of course, easier said than done... If you already have a pet cockatrice, bring it and let it take on the wild ones! Like wolves, they attack the mobs that you target or that have targetted you, and cockatrices have many advantages over wolves when it comes to battling. However, if you don't have a pet, then craft up a blindfold, put it on, and slay the cockatrice the old fashioned way (potions and enchanted gear is recommended).
Death worms are a bit tricky with their digging ability. BUT, they have a huge disadvantage when it comes to the Xeric Shrubland; there's dirt, and quite a bit of it everywhere. So, if you don't want to deal with the worms, stay on the dirt patches, because they can't dig through it opposed to sand! This can also help you kill them; lure them onto a dirt patch, and go crazy with your weapon of choice, since they can't escape.
Now, myrmex are a whole different story... there's many ways to take them on, some much more difficult than others, and it depends on whether or not you've conquered or found another myrmex colony elsewhere. I could go on all day about the different ways to take down or rule over myrmex, but this post is already quite wordy, so I'm afraid I'm gonna end this one short. Experiment, I suppose, see which way is easiest for you!
I hope any of this is helpful to whomever reads this post. Good luck to those venturing out to find the Xeric Shrubland, and respect to those who differ...