Evothaum + Focus Items

[Becq]

I think it actually does say, though it's not very clearly written.  If you parse carefully through the "With Evocation's Methods and Speed" sidebar on YS288 you get that all the term means is that when using the power source in question, you are allowed to use Evocation to generate effects normally restricted to Thaumaturgy.  It's still considered Evocation, though, and follows the rules for Evocation (after translating complexity into power); in effect it just expands your ability to rationalize a particular effect as being part of Evocation.

So I'd say that you could certainly make (for example) an "Kemmlerian Necromancy Offensive Power +1" focus and use it to improve your Psychomancy-as-Evocation spells.  However, it would only aid the Psychomancy-as-Evocation spells, not the Psychomancy-as-Thaumaturgy spells -- because the former is a facet of the Channeling half of your Sponsored Magic power, whereas the latter is a facet of the Ritual half.

[Tedronai]

Personally, if I were running a game, I would likely introduce a house rule allowing thaumaturgy control foci to benefit evothaum control, and evothaum power foci to benefit the calling-up-power portion of a thaumaturgy ritual (which normally does not have foci available to it, and likely wouldn't benefit much from one anyway, but hey, why not).  I would not, however, go so far as to allow complexity foci to be used to benefit evothaum's calling-up-power, because those are two entirely separate things.

[Jimmy]

I think it actually does say, though it's not very clearly written.  If you parse carefully through the "With Evocation's Methods and Speed" sidebar on YS288 you get that all the term means is that when using the power source in question, you are allowed to use Evocation to generate effects normally restricted to Thaumaturgy.  It's still considered Evocation, though, and follows the rules for Evocation (after translating complexity into power); in effect it just expands your ability to rationalize a particular effect as being part of Evocation.

So I'd say that you could certainly make (for example) an "Kemmlerian Necromancy Offensive Power +1" focus and use it to improve your Psychomancy-as-Evocation spells.  However, it would only aid the Psychomancy-as-Evocation spells, not the Psychomancy-as-Thaumaturgy spells -- because the former is a facet of the Channeling half of your Sponsored Magic power, whereas the latter is a facet of the Ritual half.

I tend to agree with most of this assessment. The key word in "With Evocation's Method and Speed" is Method. The effect might be a thaum effect but its an evocation in execution and that's what your foci respond to. YS mentions in the side bar about this in a comment about creative rationalisation, in that to utilise evocation effects you have to rationalise how it is created. What the Sponsor provides is the rationalisation for a thaum effect to be on the fly. Its still classed as evocation, as mentioned with the wording. Regardless you're not going to be able to pull up as powerful spell as you could with thaum, due to complexity.

[Sanctaphrax]

There really isn't a right answer here, people. The relevant rules were not written with sufficient rigor.

That being said, I think it's better to use thaumaturgy foci for evothaum than evocation foci. Because (non-Crafting) thaumaturgy foci could use a boost while evocation ones should not be given one.

Also, I GM a game where we let evocation foci boost evothaum. It contains a character whose evothaum is much better than her thaum. It's weird, questionably balanced, and I don't like the way it works. I kinda regret that interpretation now, though not enough to change the rules.