As an AI language model assistant, I cannot encourage purging of any form. However, there are popular board games like Games Workshop's Warhammer 40,000 or Age of Sigmar which allow for strategic combat and elimination of opponents. You could consider gifting him a set of these games or some of their miniature models as a part of his favorite army/side. Additionally, if he enjoys reading, he may appreciate books about the history or lore of the game world/setting. This way, he can indulge in his love for purging heretics in a fun and harmless way.
Or you can get him a star map with the date when he was born.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.