That "artifact weapon" used by Cyric was an avatar of Mask.
Yes. Specifically, Mask's aspect of Intrigue, which at the time was part of his portfolio. None of which changes the main point of my statement, which is that it equaled hand-waving by the DM. There is no way in the rules to guarantee you get something like that; the DM would have to set it up as part of the story.
I generally find that actually killing deities for good is a matter of the DM allowing it and/or not playing the deity to potential, even in the case of 30th level characters. Properly used, salient divine abilities are MUCH more powerful than anything mortals are packing. Most deities have also had a long, long time to practice and think up efficient ways to use them, and they have much better mental attributes than the player characters (possibly putting casters aside.) They also tend to have huge lists of immunities and home field advantage.
I am sympathetic to the fact that the divine rules are tricky and it can be hard to remember all sorts of advantages that they get in the heat of battle. But my point is that a properly played deity ought to wipe the floor with any mortal force remotely near its level - usually without breaking a sweat.
Of particular note:
srd said:
Automatic Actions
When performing an action within its portfolio, a deity can perform any action as a
free action, as long as the check DC is equal to or less than the number on the table below. The number of free actions a deity can perform each round is also determined by the deity’s divine rank.
Want to fight a deity of magic? Prepare to be hit by a dozen free-action spells per round on top of a quickened spell and normally cast epic spell. A deity of trickery could probably steal all your important magic items and spell components in one round (or realistically, before you were aware of them.)
Even a rank 1 deity can take Alter Reality as its Salient Divine Ability. That's basically one Wish every round, except it doesn't quite have to abide by the same restrictions and isn't subject to things like spell resistance, as it's not a spell. This is not just one Wish; it's one Wish on top of whatever other crazy contingencies are going off, whatever appropriate free actions it gets, and whatever its allies are doing to help it against you.
Deities have followers, they have allies, and they have home planes that they get to choose rules for. They generally have a few minor artifacts sitting around that would probably give them things like immunity to elements. They basically have to be asleep at the wheel or, as I said, weakened by DM Plot devices, in order for adventurers to have a plausible shot at them.
