Here we are again, with another Q&A session with your favorite sorcerer. :)
How are deities affected by worship? Do they gain strength from it? Do they need it to survive?
Does the loss of worshipers weaken them?
Yes, worship does certainly provide energy to those on the receiving end, and of course, the loss of said worship does remove some of the power the spirit in question appreciates. One could say that the loss of worship is a demotion of sorts. However, any spirit worth their salt is not stopped by that. There are plenty of deities who have been around for so long that the power they've got stored up is monumental. This is particularly true of those who tend to stand outside the passage of time, such as Mahakala or Kali-ma.
Other "lesser" spirits would be more affected by the loss of such following. Land spirits for example, are devastated when people steal their energy. They often lack the means to replenish it, and that's when offerings are useful. Servitors behave in the same way, insofar as if they are not fed enough, they will find their own means of obtaining the energy necessary for their survival.
You've made mention of the fact that some spirits are able to cross between pantheons at will. Which spirits can do this?
That's all for now.