Hints and direct spoilers to all easter eggs / bosses

[Cooper]

Graveyard

Hints

Nothing found:
Somewhere there is an item you can use to find another item (and a music disc too)

Rope and cup:
One of the classes may have something sharp to cut the rope with...

Pillar blocking cave:
It looks breakable with enough enhancement.

Disc player location:
Hidden in the cave in a corner.

Stone throne:
there is an item you need to steal from someone...postmortem. Place it on the throne once acquired. To revitalize it, it requires sacrifices.

After boss 1:
The skull reappeared, there is something... magical in the graveyard that might want it.

After skull:
Something else has appeared on the map. It seems to require a key...

Seed:
There is a nice plot of land to place it. Wait a few rounds and see if it grew.

Pumpkin:
The potion is not complete.

After boss 2:
The witches came to protect their brew, but it was not completed. They forgot to stir. Something has appeared in the graveyard allowing for this to happen. When the brew is finished, something should rise from it but it requires sacrifices...

After boss 3:
A portal spawned somewhere, but it requires a toll.

Direct spoiler

Nothing found:
There is a shovel between the coffins next to the exoskeleton upgrade. Take it and find 2 dirt piles in the graveyard. One has a skull and the other has a music disc (not required for progression. Just plays the best song ever)
First pile of dirt: Go to the exoskeleton upgrade, turn right, and follow the wall. it is on the same stretch of the wall right past the health upgrade (the red circle of light)
Second pile of dirt: Go up to the barrier to the spooky house like you are about to enter it. turn right and go past the stone square, past the exo boost upgrade (yellow circle) and go about 5 graves ahead and you should see it. It is between the upgrade and the ghost spawn point if you look at it from the side.

Rope and cup:
Upgrade the ninja to the highest level and cut (what used to be punch (right click)) on the rope. the key should fall with the cup to the ground. The rope and cup are in one of the trees (not hard to spot). The rope goes from the ground up into one of the branches, suspending the key.

Pillar blocking cave:
You first need to purchase the exoskeleton. The entrance is right next to the exoskeleton upgrade.

Disc player location:
Beneath the stairs.

Stone throne:
If you have the skeleton skull, approach throne and place it. The boss should spawn after you kill some ghosts near it.

After boss 1:
Take skull from throne and go back up the stairs to the cauldron next to the spooky house. Place skull inside. A chest should spawn in the entrance/exit (stand in the corner with the cauldron and turn right, follow the wall until you reach it).

Chest/seed:
Open the chest with the key from the rope and the cup. Inside is a seed, take it and plant it in the stone square near the cauldron. It will take 3 or 4 rounds to grow. When it is fully grown, take it and put it in the cauldron.

After boss 2:
start in the corner with the cauldron and turn left. Follow that wall to that corner. In that cornet there is a bucket with a spoon in it. take the spoon and stir cauldron. This will spawn a floating pumpkin. It will move and then stop in a spot. You need to kill some ghosts near it and it will move again. Repeat until boss spawns.

After boss 3:
A portal spawned in the entrance. You need to pay it 4 installments of 5000 points. (20,000) total.

Dark Castle

Hints

Electric gate:
Hidden behind the fallen is the key to the bridge leading to what I will now call the island.

Key to castle door:
Past the bridge somewhere someone left the key out in the open.

Exoskeleton suit location:
In the castle there is a part to activate the mechanism that lifts the large wooden door/pallet/floor. On there is the upgrade.

Music disc location:
Near the throne, the king likes his music. The player is on the island.

To fight first boss:
There are 3 heads around the map. 2 in the castle and 1 on the island. You must first enhance yourself in order to activate them. One all are active, go to the courtyard where the larger head resides. Sacrifice ghosts to summon it.

After first boss:
Something appeared in the room where the werewolf came from. It requires sacrifices to keep it going. follow it until it disappears. Flick the lever to the machine it powered.

After second boss:
The monster left something behind... the king might want it! Leave it as a present on his throne. Sacrifice ghosts to the "present" until it changes. You might as well stab something else in the room while you're at it.

After third boss:
Once the Count was slaughtered, the magic hiding his sacrificial circles has vanished. You see at least 4 all over the map. What was he trying to summon?

After Lilith:
A portal spawns nearby, but it requires a toll.

Direct spoiler

Electric gate:
Behind the fallen statue near the exo boost upgrade (yellow circle) is a lever. Take that lever and put it in the box on the wall to the left of the gate. Press f again to turn the gate off. This opens the bridge to what I will now call the island.

Key to castle door:
On one of the tables on the island. Silver, not that hard to spot.

Exoskeleton suit location:
In the castle, on the 3rd pillar to the right is a part to a lever contraption. Take the part and go to the island. To the left of the tables is a place to put the lever. Place and activate it to raise the exoskeleton.

Music disc location:
To the right of the throne, still on the platform its on, is the disc. The player is on the island.

To fight first boss:
There is a head on the left of the pedestal the throne sits on, one on the left interior wall of the castle, and one right above the small trapdoor on the island. You need to have the exoskeleton in order to activate them. You need to attack them and see that they are glowing red in order to know they are active. When all 3 heads have red particles in their mouth, go to the courtyard. There, you need to kill a bunch of ghosts to spawn the werewolf.

After first boss:
An electricity ball spawns in the room with the werewolf. Follow it and kill ghosts near it when it stops. it will disappear on the island on top of the large lever directly in front of you when you come off the bridge. Pull the lever to awaken the 2nd boss.

After second boss:
A heart appears in the tube where he spawned. Take the heart and place it on the throne. Sacrifice ghosts to it until it becomes a dagger. Take the dagger and stab the crucifix on the left wall of the castle.

After third boss:
A magic circle will appear to the left of the door (as you are leaving) you need to sacrifice ghosts to it. Another one will appear where the werewolf spawned. Same deal. 3rd one will spawn right as you are getting off the bridge to go to Frankenstein. You get the gist. Final one will be in the courtyard. Finish it to summon Lilith.

After Lilith:
A portal spawns in the entrance to the courtyard. It required 4 installments of 5000 points. (20,000 total)