Some curses are not meant to punish, but rather test those who receive them. The characters who willingly submit to such a curse have two options- have it removed by magic and return to a normal existence (thus failing the test) or go on a quest that will relate to the curse’s effects. If successful, the curse is lifted and the character gains some sort of reward. Here are a few examples:

The recipient is transformed into a kobold. The quest is to integrate into kobold society, find and fool an elder shaman (the equivalent of a high priest) and steal a relic from a major temple. Upon holding the relic and seeing the sun rise, the character is returned to normal and gains all the positive kobold racial traits.

The recipient gains an allergy to armor of all kinds. Wearing such weakens the character, making them physically ill. The quest is to retrieve an ancient helmet from a magical culture long gone. Their ruins are filled with traps that armor protects against (at least partially). Once the character places the helmet on their head, the curse is lifted and they gain an armor class bonus and an improved initiative, both useful against traps.

The recipient gains a fear of the dark. Any time they are without light, they must save or run towards any light no matter how foolish that may be. The quest is through an unlit dungeon where glowing stones draw the unwary to their doom. Reach the bottom most vault and take one of the torches and the curse is lifted. The character can Dispel Darkness and produce Light at will.

The recipient is hated by nature. All animals run or attack from them and plants Entangle or worse. The quest is to destroy a major aberration, such as a beholder hive mother or aboleth ruler. It is within an area where the aberration’s nature is transforming the natural world, making it dangerous to all but the aberration and its kin. The character takes additional damage or penalties to their saving throws in such locations while cursed. Once the deed is done, the curse is lifted, the land starts to revert (this may take months or years to complete) and the character gains the ability to transform natural goods into gear. They are never without armor, weapons or tools in a wilderness location.

The recipient is deformed, scarred or visibly diseased. They must travel to a royal court, maintain a presence for 1-4 months and obtain favor from the king and/or queen. Once the time limit has elapsed and the favor gained, the curse is lifted, the character gains a bonus to efforts of diplomacy and becomes an heir to a formerly dead noble lineage.