So here's a run-down of the levels, approved by Jonathan. WARNING LONG POST INCOMING!
Some light lock-and-key puzzles, but mostly straightforward. There will be several sub-areas (not like 'world 1-1', all part of the same level, going straight into eachother), with the last being a small trash-dump area where you'll fight baby Doldrum. The enemies here include gromory, bumpty, scravenous, and mumblegog among others. Most keys are guarded by pestequirms (which are surprisingly dangerous).
Mortasheen City Sewers:
The obligatory water level.
To avoid frustration, there won't be annoying, unconventional water controls. One third of the level will be on land and the rest will take place underwater. The boss is a large vermoeba which you defeat by taking out its heads. Enemies include funguslyme and scumbat (for abovewater portions) and necrozoa, octopire, and others (for underwater portions). Debating on whether or not to make a breath meter.
Mortasheen City Streets:
A bulk of the level is jumping from big truck to big truck (there are trucks in mortasheen, right?). Some trucks have puzzles to complete before you can board them, like cutting a rope to let down the platform or using a special mechanism to leap onto the truck. The boss of this level (a gullywunk in the back of a truck) is defeated by weakening it enough to hit a switch which send the truck crashing into a nearby building. Enemies are mostly bioconstructs and biomecha.
Harlequeen's Carnival: You start in circus tents filled with Joker types and eventually move to the meat of the level; the 'attractions'. Planned is a funhouse which screws with your controls and/or interface, a ferris wheel where you get the devilbird egg, and a test-your-strength attraction to get the boss key. The boss is Harlequeen, who spends most of the battle spawning mooks. Obviously, the enemies are primarily joker types.
Like the city streets, most of the level is spent jumping from vehivle to vehicle, although this time its tanks. Some tanks have cannons you can man and use to shoot enemies or break down barriers. These cannons are also pivotal in the boss fight. There are no actual enemies aside from the cannons and guns on the sides of the tanks. The boss is the biggest tank, which you beat by shooting down with allied cannons.
In this level, you'll spend a lot of time either walking along the backs of the larger corpses or 'swimming' throug the smaller ones. At one point in the level, you can take a detour and raid a zombie pirate ship to get the devilbird egg. On the ship are cannons and, of course, zombie pirates. It's a fairly straightforward level. Boris is the boss, and you defeat him by climbing all over his bloated body and attacking weak points (giant cysts) while avoiding acidic projectiles and the festerlings it spawns from its headstones.
The final level takes place within axabod himself, where you trek through visceral corridors and organic rooms. Some puzzles in the form of cutting veins or popping blisters are littered about. Mostly arthropoid monsters dwell in this level. Again, no real twists aside from light puzzle elements, although you can do some exploring throughout the level. Axabod has the only two phase boss fight in the game. You start off fighting axabod's giant womb, which continually spawns arthropoids, shoots tumour-bombs, and tries to knock you into the acid below. Once it takes enough damage, the womb bursts to reveal a gigantic Chimerisect inside. Smaller wombs still spawn enemies, along with the chimerisect spitting projectiles at you and trying to devour you. Once you beat the chimerisect, axabod's insecile immune system is distracted for long enough to escape, and that's the end.
BONUS LEVEL: Unknown Dimension:
NON EUCLIDEAN GEOMETRY AND UNKNOWN TYPES.
FIGHT THE NULL.
DIE A LOT