The area affected by the spell source severance is a "5-ft.-radius emanation, centered on you". What squares on the grid does this affect, if you are a Medium creature? Just yours? Yours, and the the four squares orthogonal to you? Yours, and the eight squares around you?
What squares does this affect if you are a Large creature? How about if you are a Huge creature?
Now, suppose you are a creature with some spells active on you, standing adjacent to a creature under the effect of a source severance that would suppress your spells. If you are a Large creature, does the source severance suppress your active spells? How about if you are a Huge creature? Does the answer to these questions depend on how many of your squares are in the area of the source severance?
Source severance affects you and 5' around you, regardless of your size. FAQ.
Less absolutely - being partially within an area of effect is generally sufficient to be affected. There are some exceptions involving line of sight, but I think a large+ creature which is partially within the area of someone else's source severance will be affected, the same as if they were fireball'd.
That's very helpful, avr - thanks! I hadn't seen that FAQ. So what it's effectively saying is that a Medium creature will actually affect a 15-foot-diameter sphere with source severance.
Yep. Or a 15' cube, practically speaking.
I don't think I'd include the corners of a 15' cube in the area affected - but that's not going to make any practical difference the vast majority of the time!
I see what you mean about the FAQ, Jeff. So, your view is that source severance on a Medium creature will affect the creature's square and three other squares around one corner of the creature's square? I can see this point of view, based on the general rule that "The point of origin of a spell is always a grid intersection." However, I see that rule as being trumped by the spell's specific definition of "centered on you". So I think it's probably best to use the FAQ approach for Medium creatures, too.