I looked on the boss page and there's no event bossses added to the Wiki yet. Margrel, the first event boss from Moorcroft Manor so far, hasn't been seen on the boss page yet. Can someone take care of this please? Thanks!
Did anyone forget to add the event bosses?

Margrel is mentioned at the Kat article. Feel free to mention it at the Boss article. Go ahead.
I know. I could do that, but I didn't get the chance to encounter Margrel yet, so I'm not sure. Besides, I'm referring to anyone else who did battle Margrel. If anyone did and defeat it, and chronicled it's attack patterns, please edit the Wiki.

Well, I've beaten it, and I have video, but there is also video on YouTube, if you're really interested in describing Margrel's AI in the Boss article. Basically he teleports around, and launches nasty black kats and zombies, and curses you (or something does), and he's generally rather a jerk.
Edit: I've added an entry, albeit without a list of his attacks.

http://wiki.spiralknights.com/Kat#Margrel
Move that around, if you want.

Oops, thanks. I just copy-and-pasted that in. I'm not sure that having duplicated information is desirable, but there it is.

It's ok since [[Boss]] is a summary page, so it's perfectly fine to have duplicate information there (The information there for the other bosses you could find on the bosses' main page too)
Warmaster Seerus is an Expansion Boss, and Margrel is an Event Boss. My apologies, but they are not supposed to have the summary label "Other", because it makes no sense. Margrel is supposed to go under the summary "Event", and Seerus should return to the "Expansion" summary in the Wiki's boss page. Get the picture?
I'm sure I could do the Wiki editing, but I know anyone else can, too.

It's a matter of taste, but in my opinion the Boss page was overly micro-classified. Basically, if you are trying to classify some objects (in this cases, Spiral Knights bosses), and you end up with a bunch of classes that contain only one object each, then your classes are too narrow and specific. So I have gone through the Boss article and merged classes. For example, there is now one class for the four regular Clockworks bosses, instead of splitting these four objects into three micro-classes based on tier.
Yes, Seerus is from an expansion and Margrel is from an event. But there is no reason why each of these things deserves its own class right now, because there is only one object in each class. Until Three Rings comes out with a couple more expansion bosses, or something like that, then a catchall class called "Other" or "Miscellaneous" makes sense.
Edit: Alternatively, we could move Seerus into the Missions class. He makes more sense there. Then we are left with Margrel in its own class, which could be called "Other" or "Event" if you prefer.

we could move Seerus into the Missions class
Twas what I was thinking, but it's not a big deal (to me, that's why I didn't change it ^_^)

Done. Maybe now this not-very-enlightening discussion can be concluded?
I was making sure to keep the Wiki Knights sharp on some details, so that will do. If there's another new event boss added or otherwise, be sure to update the page. Thanks, though.

I havent played SK for about 10 months, is Margrel permanent?

Yes, but he is only accessible with a book of dark rituals.
What? Margrel is a boss for the Kataclysmic Confrontation event, so shouldn't Margrel be in the boss page?