Best ways to kill a Tier 1 caster without being one

[Tiki Snakes]

Why not just use wish to cast forbiddance? Or better yet, gate in something to use wish for you or use shadow conjurations. It might be slightly more pricey, but it is undeniably legal and accomplishes the same thing.

EDIT: Or do what Tippy suggested, as it sounds way more fun.

I'm unsure, but I think that is why Tippy = Win.