Best ways to kill a Tier 1 caster without being one

[Baron Corm]

Oh, like him being on a demiplane you couldnt gain access to with the help of a deity

I'm afraid I'm not familiar with the method of doing this. Could you be more specific? Also, what Jolly said. As far as being able to influence the Material while doing this...

Astral Projection. A Simulacrum of yourself plus a Permanent Telepathic Bond with it.

A wizard can interact without any problem, even when remaining in a secure location.

For day to day stuff and other activities that aren't likely to gain you experience; Simulacrum's are your best bet. Sure they are half your level, but that is still 10th level at level 20. More than enough to handle day to day affairs at court or in a city. When something more is needed your Astral Projection can arrive quickly and easily.

If you find their astral projection, sever the silver cord, and it will kill the wizard himself as well as the projection. Otherwise treat as normal wizard. The simulacrum is not a real threat, having half of your class levels. This still leads to the scenario of the wizard just sitting around being non-threatening in his demiplane/"court". So what else?