There is one Witch Talisman and 2 Witch Quests:

Step 1 - Level: Cemetery Hill (Witch Talisman): First you must get the "Witch Talisman". It's found in Level: Cemetery Hill. On the hill with the rolling rocks you can jump down the left side to find a hidden chest with a club weapon inside. Use the club to smash the big boulder to the right of the starting area. This leads to the witch cave. Put the club on fire by holding :circle: near a fire source, then light up the object in the middle of the prison cells, inside the witch cave. This opens the prison cells, the Witch Talisman is found in there. It's the same place as this level's Chalice location.

Step 2 - Level: The Enchanted Earth (Quest #1): Use the Witch Talisman on the green Cauldron in Level "The Enchanted Earth". You do this by opening the inventory with Touchpad :tp: near the cauldron. Accept the quest the witch gives you. She shrinks you and puts you in an ant cave. Once in the cave, grab the club weapon from the chest, then destroy the wall on the right side to find a fairy. The fairy opens the portal to the ant cave. Your job is to find 7 pieces of amber which are guarded by the ants. After getting 7 pieces of amber, destroy the big amber glass wall at the end of the cave (there's a readable book there as well). Then drop down behind this amber glass wall to the Queen Ant boss. Defeat the Queen Ant. Afterward you get ported out of the cave and the Witch Quest is done.

Step 3 - Level: The Pumpkin Serpent (Quest #2): After defeating the Pumpkin King, backtrack to the start of the level and use the Witch Talisman on the cauldron twice in a row. The Pumpkin Witch will first tell you she wants you to kill the Pumpkin King. On the second summon she thanks you for defeating this level boss and gives you a Red Gem, as well as the trophy.