[Slydria]

Well, I imagine something like this would be possible. I think it probably makes sense as a specially crafted magical tool that emits this field.

Limitation wise, I'd say there's some things to consider:

- If the field is spread too thin, the effects would be diminished or eventually useless. Keeping it to the dimensions of say a large house would probably be fine though.

- Eventually the focus source will run dry. You'll just need to swap that source out every now and then.

- More youkai summoned would mean a faster focus drain and thus shorter field lifespan before needing to replace the focus source.

- Being a magical feature that essentially provides focus, I imagine it would be rendered useless by dispel or interference magic directed at the source.

- You'll still need to be within summoning range for your Youkai to be maintained, even if they're drawing on the field instead of your own focus.

Assuming that's all fine, I don't have a problem approving this.