Of course, there are exceptions to any rule. Now and then a young mer will put their heart before their head and sometimes the union is blessed with children. These forbidden children cannot be brought up in mer society and so they usually grow up on land, knowing little of their heritage.
Half-mer look entirely human but can usually take mer form if immersed in water. They often have Illusion magic and can express magic in the same way as fully-human mages.
FOR PLOT REASONS WE ARE NOT ALLOWING HALF-MER PLAYER CHARACTERS