The mission would primarily be themed around the sea and be know as "Horrors of the deep". It would be very similar to other areas until you enter a water themed area, here bullet speed and attack speed will be reduced somewhat and new water themed monsters would lurk here (possibly scuba wolvers :D). After 4 difficult water areas the party of knights will face The Kracken, after defeating 6 of its legs, the beasts head will be visible and attackable (if not killed fast enough the legs must be defeated again. Upon defeat it will yield an appropriate amount of "Sea minerals" these will be the tokens used to buy the following equipment.
Ghastly Constraint
5 Star sword shaped like an anchor, only darkened and rusted. Normal/Shadow damage mix, around the same as Gran Faust. Powerful AoE charge with stun chance.
Captain's Flintlock
4 star gun, pure normal damage. Appears as a standard flintlock until upgraded, explosive charge.
More to come, tell me what you think.
Before going any further one thing must be made perfectly clear. If someone can not read your full post and think "TL;DR" then it is not long enough to be a new boss. "Hurr a boss that is in this kind of place and looks like that and does these things." You can do better than this. What are you waiting for, a hug? Before you reply to this post, yes, I always criticize and analyze every thread I believe needs it. Does that mean the thread is bad? No, it means you are trying to build a house with two bricks; you need more to it. I am willing to help you though I am not always available all the time. It may seem I am always there when no one wants me but that is because I can read your mind.
"Horrors of the Deep"
Sounds like a bad shark based horror movie.
Water theme? Is it underwater? Believe it or not we do not have a water themed area in this game yet because it does not exist; there is no "water" status. We have water blobs to remove hotspots which players can not move through. The same blobs also extinguish players if the blob "explodes" with the aflame knight in its area of effect, which is fairly small.
Wolvers underwater? What are they, amphibians? Make some fish enemies, everyone wants to see that. No one wants to see things we already have with scuba gear. That is just silly.
"Three difficult areas", how very in depth and specific. We know you can do better. Describe the layout of the floors, which enemies appear in certain areas, et cetera. "But replier this is just a suggestion no one reads these and I do not have to give details, hurr." Nurp. Do you know what Howlitzers and Polyps are? Guess where they came from?
A Kracken, how "original". I know there is not much to work with in terms of undersea enemies, but a giant squid; there are more threatening things down there. I would link pictures but some readers are not of heart for such images. At least there is no shark. Contrary to common belief sharks only attack when they think you look like food or are bleeding. Coastal sharks only go for surfers in wet suits because they look like otters. Sharks actually hate the taste of human. Sharks have a strong sense of smell, meaning when blood is about the sharks cometh. This is because when something is bleeding it is assumed to have been crippled and/or recently killed, meaning fresh meat with less difficulty to consume. Sharks do not swim around going "derp herp I bite you hurr". Enough of this nonsense, there are more important matters to be dealt with.
The boss, it needs far more detail. It needs to have about as much as this entire post, just for the boss. A T3 boss has to be that complex.
Token rewards, usually the last part of every boss suggestion thread. What is this? New weapons without explaining the mechanics? Either recycle existing mechanics or go in depth with new ones. An anchor sword is obviously large and heavy, it can be a heavy two swing combo. Make this an upgrade line where the 2* or 3* is a token reward for 15 or 20 tokens so people will want to do Clockworks for the recipes to make it 5*. As for the gun, this needs a lot more detail. Again, 15/20 tokens for the 2* or 3* to encourage players to stop spamming Vanaduke and get back to the Clockworks.
I am particularly fond of the anchor, especially since it does shadow. We need more shadow weapons. I recommend making some art for the weapons, boss, and possible parts of the floors.
If you decide to make more I will grade it thereafter.