Tri is right on, as usual.
In one of my groups, they have an Artifact weapon and just learned the joy of AMF and that fighter going OFF on enemy spell chuckers.
I mean, he's a level 19 Fighter trained to cut things DOWN. Once he's on you and you have none of that fancy pantsy magic... yeah, pain. Lots of pain, for one round that is.
Ok, just for clarification. You can cast spells with the staff in an antimagic field?
This is an interesting question, because the moron who casts antimagic field to then blast things with spells is in serious danger (beware with angry DMs) ;)
The description about antimagic field states: "Artifacts and deities are unaffected by mortal magic such as this"
I think that after the spells are casted, no longer are part of an artifact... because, you know, fireballs in an antimagic field? I´m not sure... The spell resistance and the retributive strike yes, but spells not.
Its a disturbing question, yes. I have a moron master who send an Amazing Red Wyrm against us with a funny antimagic field, with an artifact you probably could defend yourself with that kind of item.
Queen Ileosa had a runic pool that shares freedom of movement with her. In my opinion you can use spells in the antimagic field but, for example if i play with an eldritch knight will be a lame thing casting spells like a coward when you can hadle your great elven sword agains the bad guy.