Snakes! They will sneak in at you, they will eat all your leaves, all your peat, and you'll be horrored! Cut them (violently) to get cobble. They also poop lode.
(Seriously, they are very scary and this mod is very violent)
I run this mod on a family private server (where the gameplay is less "hardcore" than vanilla) and it's a nice and very natural-feeling extension of gameplay. It changes the gameplay balance, especially making ongoing lode supplies much cheaper, but compensates nicely by adding an engaging snake feeding and caretaking system.
UPDATE: I'm revising my criticism, because, at least since the addition of Forms to the game, it is highly feasible to catch a snake and trap it in an enclosure that ensures it stays safe and healthy indefinitely, as long as the player remembers to keep it fed, which is not an error-prone process. Leaving design of such an enclosure as the player's responsibility is consistent with the challenge level of NodeCore.
In addition to less self-trapping behavior, richer pathfinding interactions might be nice, like certain kinds of nodes it avoids (igniters, radioactives, metals?)
Reproduction/renewal mechanics, such as laying eggs if fed certain high-value resources. It would be nice to be able to keep dormant eggs in storage until needed, and then incubate them somehow to hatch them, esp. as mitigation for snake fragility. (There's a "skyblock recipe" that allows making one from nothing, but a more natural way to expand a stock of them once you have one would be nice)