Monsters work their way into our hearts in tons of ways. Some have art that grabs you immediately, some fill a niche you need in a campaign, some fight players in epic battles, and some have a tiny throwaway line in their monster entry that justifies the whole thing. But even with all that, I think these monsters made it to the list somewhat uniquely.
Kruthiks are reptiles, but you’d be forgiven for thinking they’re insects or weird chitinous dogs with spider legs. They best analogy I have is that they’re low-level Zergs. They happen in swarms, they’re startlingly fast, they can burrow, and the bigger ones even spit acid. I think they were first published in the catch-all Minatures Handbook, which seemed to contain monsters and classes Wizards wanted to make into miniatures but couldn’t because they hadn’t published them yet. They were justifiably forgettable until they were included in the 4E Monster Manual, where they got a little bit of lore that made them acceptable minions for a low-level villain or antagonists in a short adventure.
I didn’t care about kruthiks, at all. They didn’t seem fun, they didn’t seem unique, and I played Protoss anyway. I did collect D&D’s randomized miniatures, and while I didn’t want kruthiks I could use them as stand-ins for other things. One day I looked at my collection and realized I had six small kruthiks, three medium ones, and a large. I figured I might as well do something with them. At that time my campaign was already nearing epic levels, so the bottom-tier kruthiks didn’t appeal to me. But I could take how they looked, strip out the stat block, and use them an inspiration for something decent (so take a drink of a different beverage, I guess).
Scientivores were creatures that ate knowledge, in the same way that herbivores eat herbs and carnivores eat carnivals meat. I don’t know why I settled on scientivore instead of cognotivores or librivores, but that’s not important. The players met them in a demiplane made entirely of library, and the scientivores were slowly consuming the entire dimension. Unlike most monsters they weren’t a threat to the players or their allies directly, but defeating them was the mission the party had to accomplish, and nobody wanted to find out what would happen if they ate all the books and realized there was information in brains too.
They worked well, not least because of 4E’s excellent minion mechanic. They could swarm the party while still being a threat in a way monsters normally can’t. The first time they attacked, the players got a map of the area and five rounds’ warning so they could shore up and build their defense. The scientivores smashed open doors, burrowed through walls, and worked the party into a corner before reinforcements arrived (which, in retrospect, may have included Eligio). After the party fought them off, they developed a plan to destroy the entire hive at once, and that’s how we got this story.
The way they fell is still one of our favorite stories, but that only worked because they were viable enemies even before they first came onto camera. I still didn’t run a kruthik proper, and I probably never will, but without the creature and its miniatures we might not have had a library at all, and I’m pretty sure that ended up being one of my players’ favorite floors in that campaign.
To me, Kruthiks always feel like Ankhegs that have been given the “reptile” keyword. I sometimes think about removing that keyword and just using them as a variant Ankheg.