Snarbolax. Jelly. Twins. Vanaduke.
Spiral Knights' main quartet of boss monsters certainly isn't lacking. Every one of them presents a significant challenge along with its Shadowlair counterpart(s).
Seerus. Herex. Maulos. Iron. Margrel. Sentinel. Collector. Punkin.
This assortment of mini-bosses doesn't disappoint either. However, this scattering, while far wider, is much more rare and usually less rewarding to battle in terms of payout. As a result, there are only so many challenges available to us at once.