Board Thread:Episode Discussion/@comment-24993958-20161231141844/@comment-30869555-20170101030040

I think that the reason Tyrian was willing to use lethal poison on Ruby was that he had a antidote and after the poison done enough damage, greatly weakening her to the point were she would have trouble moving(and it likely would have greatly weakened the amount of aura she had), then he would have given her the antidote. This would explain why he was willing to poison Ruby when it seems to be killing Qrow.