[skippyboxedhero]

Because the function of the spell is to modify the state of the wizard, the wand, and the goblin...that isn't obvious or correct. It can go on the wizard, it can go on the wand but the problem is that the solution is very brittle (because you will likely end up with inheritance as you add other objects). Again, the key point is that in OOP these cross-cutting concerns will likely end up with a design that is complex/arbitrary/unperformant.

This is a good tutorial on this topic - https://ericlippert.com/2015/04/27/wizards-and-warriors-part...