You can find the manual of the game in the "extras" folder.

Manual/Tips of the game:

In the "Exploration" mode, you will begin each episode in a central hub map with access to 4 other maps.
You will find keys to open locked doors along your way.
After approaching a lock, your Quest Journal will provide hints on where to look for the key.
Once you have the keys for the blue portal, you can exit the hub.

The "Action" mode is similar to Exploration mode, but keys will only be required to unlock the blue portal and exit the hub.
Each map in the hub will hold one key.

In either mode, completing a hub will be followed by two maps in linear sequence, including a boss battle.

The expansion contains no hubs, and all maps are in linear progression only. Find the key to exit each map!

Once you have the keys to unlock the ending blue portal, you
can exit the hub. The keys you have collected will reset when you
complete a hub.

Items description:

_Blue Flask: +10hp, not stored in inventory (used on pickup)
_Red Flask: +20hp
_Yellow Flask: +100hp, can heal player up to 200hp max
_Ghost Head: Semi-Invisibility for a short time.
Enemies are less likely to notice you and will shoot with reduced accuracy
_Crystal of life: If the player dies, he will be resurrected at the beginning of the map with 100hp and brief invulnerability.
_Berserker Head: You will take half damage for a short time
_Berserker Hand: You will inflict double damage for a short time
_Torch: Brightens the player's view for a short time
_Mapscroll: Will reveal the level's complete automap (Default key: "Tab")
_Hand of Necromancy: Revive the enemies and make them your minions, they will fight for you.

Weapons of the Necromancer:
(Primary and alt fire)

_Magical Sword:. It can be used without ammo, but damage will be doubled with ammo.
ALT (alternative attack) is deflection of the projectiles.

_Fireball Staff:
Throw fireballs.
ALT is a triple shot.

_Ring of Ice:
Shots penetrate and stun enemies.
Falling enemies will lose flight briefly.
Produces a ring of secondary projectiles when hitting an enemy.
Enemies freeze solid when killed.
ALT is an icethrower attack who can do big damage with continuous hit.

_Tornado Spell: Pushes away enemies while dealing damage.
If an enemy is dragged along, or trapped against a wall, the tornado will do a significant amount of damage.
As the tornado expires, nearby enemies will be launched away.
Useful when near tall cliffs.
ALT creates 6 tornadoes which revolve around you and do a good amount of damage and push away the enemies.

_Unholy Grenade: A bouncy grenade that explodes after a timed delay, or on direct impact with an enemy.
Enemies that survive the explosion will catch fire and suffer additional damage.
ALT creates an explosive mine effect to the grenade, if the enemies come too close to it, the grenade explodes.

_Pistol Cannon: A powerful handgun with shotgun-style spread.
ALT activates a sniper mode with a little spread to the bullet.

_Scythe: Throws a slashwave at mid-range.
Slashwaves penetrate enemies and will set them ablaze (on fire).
Enemies killed by the slashwave or the fire will grant the player 3HP upon death.
ALT will summon a ghost who will attack the enemies.


Transformation Spells (permanent/reusable):
(Primary, alt fire and 3rd attack)

_Swamp Serpent Transformation: The player can fit into small spaces and breathe underwater.
Attacks by biting, spitting poison and throwing gas cloud.

_Stone Breaker Transformation: The player takes 30% less damage and can break walls that have cracks on them
(strike as close as possible to the center of the crack).
Attacks by punching and produces a shockwave that damages surrounding enemies or make a powerful rain of stalactites.

_Hell Burner Transformation: The player can walk on lava or swim on it without taking damage.
Attacks by throwing fireballs and produces a line of lasting flames along the ground or a circle of fire around the player.

_Wyvern transformation: The player can fly indefinitely but receives 30% more damage.
Attacks by launching an explosive fireball, throwing a short-range stream of fire or does a quick dash on the enemies, pushing them away.

Tips:

_Press "O" (default key) to open the journal.
When you approach a locked door that needs a key, a hint on where to find the key will be added to the journal.
_Stone Breaker shockwave can go through walls. Use it to kill enemies while you stay safely behind a wall!
_Wyvern flamethrower is more effective if you can pin the enemy against a wall, where they cannot pull away from you and they will take a massive amount of damage.
_Be sure to check everything and use your automap with the TAB (default) key.
You might see where to go next and if there are some places you haven't checked yet.
_To continue to play when you die, press "OPEN (default door)" key to restart.
_Press "SPACE" to open a door or activate a switch.