Get a permanent halo :
Get all the Rune Stones and then beat Skorne.
Play as the Falconess :
To get the secret character the Falconess, who has the same turbo attacks as the Valkyrie, go to the Bonus Stage in the Castle World. Get 50 of the coins there, and then select the Falconess from the Character Select screen.
Play as the Jackal :
Play through the second level of the Ice World. On top of the pile of crates, there is a trapdoor at a dead end. The trapdoor is found by climbing the slanted crates to the top, then circling around until you get a chance to go back down. From there, climb the other set of slanted crates that are located before the exit, atop the trapdoor. Inside the door, collect 50 tokens to unlock the Jackal, a more powerful form of the Wizard.
Play as the Minotaur :
In the fourth Mountain level, find every switch, and then go to the area with the exit. Instead of going through the exit, stand on the door with the skull on it. Inside the bonus round, collect 50 coins. When time runs out, you can now play as the Minotaur.
Play as the Summoner :
Get all of the shards and beat the first Skorne. Let the doors open and go to the first area. When you get to the exit, go to the left and follow the wall. You will find the gate. Get 50 Summoner coins in the area. It will be hard to see, because you only have a small light radius, so just follow the path.
Play as the Tigress :
You will have to go to the first town level. Find all the main switches and head to the portal. When you reach the portal, backtrack a little bit till you reach a hill with a chest, a switch, and Death on it. Avoid Death and hit the switch. Head in the direction the switch is pointing and you will be lead to some zombies and the trap door. Stand on the trap door and collect 50 coins to unlock the Tigress.
Weapon upgrade :
Upgrade your character to level 10, and your character's weapon will grow in size and do much more damage. This also works at levels 75 and 99.
Getting a familiar :
When you reach level 25, you receive a familiar; Valkyrie receives an Eagle, Wizard receives a Dragon; Archer receives a Butterfly; and Warrior receives a Dragonfly. Reach level 50 for a better familiar.
Better weapons :
Reach level 10 to receive a better weapon. Reach levels 50 and 99 for additional new weapons.
Permanent antideath :
Successfully complete the game to receive permanent antideath, which allows you to steal health from Death.
Good from poisoned fruit :
Poisoned fruit can be turned into regular fruit by using a magic potion near the fruit.
Find the Ice Axe of Untar :
The Ice Axe of Untar can be found in the Treasury level of the Valkyrie's Castle. This weapon is useful in defeating the Red Dragon in the Warrior's Mountain.
Find the Scimitar of Rasha :
The Scimitar of Rasha can be found in the Caverns level of the Warrior's Mountain. This weapon is useful in defeating the Chimera in the Valkyrie's Castle.
Find the Flame of Tarkana :
The Flame of Tarkana can be found in the Spire level of the Skytown. This weapon is useful in defeating the Yeti in the Ice Domain.
Find Marker's Javelin :
Marker's Javelin can be found in the Fissure level of the Ice Domain. This weapon is useful in defeating the Plague in the Skytown.
Find the Holy Savior :
The Holy Savior can be found in the second level of the Battlefield.