Arrogation
Arrogation refers to the process of forcing lower deities to do something against their will.
Methods
The methods used to achieve arrogation vary from deity to deity. It can be a very difficult process to achieve, given the powerful nature of gods, but for the same reason, it can have incredibly potent results.
A common method is forced declination - either by grounding (or ungrounding) a deity to the extent that they can no longer draw upon their powers (see forced grounding), or by nullification of a deities powers. Nullification varies in process and effectiveness by deity.
Once a deity is unable to simply utilize their powers to escape, simple reasoning is used to achieve a desired result. If enough is known about the deity, their powers may be coerced out of them, otherwise it is usually necessary to convince the deity to do what is desired.