After Thaviks disappear and goes invisible after taking damage, it is possible to see him climbing the walls on the arena. If you shoot him, he will fall off and instantly die, ending the strike
Video proof: https://youtu.be/eCRjzlDBuCY
I assume this is a cheese.
[spoiler]Video not mine[/spoiler]
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It was easier just to kill him rather than looking around for him on the walls to be honest.