What are the "Rare" Monsters found throughout the Clockworks?

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As you can see from the picture above, on the tip panel, it reads:

Rare Monsters

Rare monsters offering unique items roam the Clockworks. Have you discovered any yet?

What are these "rare" monsters it talks about? What are the unique drops? I'm not quite sure what they mean by "rare"...

Solution 1:

Well, there are monsters with an incredibly low spawn rate. One example is the Soul Jelly, seen here on the Spiral Knights wiki. While it doesn't have unique drops as far as I can tell, it's drop rate and amount is generally higher. There are other examples, like the Love Puppy, seen here on the wiki. It has the chance to drop even rarer items, including various Heart pendants.

If you want to browse for more kinds of rare monsters, go to the Spiral Knights wiki and search for the Monsters page. It lists all of the monster families, and if you scroll down to the bottom of a monster family page, you'll find notable examples of monsters in these families, including rare monsters and monsters removed from the game.

Rare monsters: