You get a tier 2. It looks like the tier 1 was popped first but I think no matter what you will get a tier 2.
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Yea we did this by accident. A random that joined us put in a tier 1 as I was using a tier 2. Seems like the higher level rune wins. Guessing the same will happen if a 2 and 3 will be used the tier 3 will happen