Erik simply listened carefully, a part of him still unable to believe what he was seeing with his own two eyes, now returned to their former gray hue. In less than half an hour this human had turned from mortal enemy to... well, he did not know what to classify Alexi Vandros now. Insane, surely. But besides that, Erik was not entirely sure if he could trust him. There was still a chance that this was all an elaborate ruse, but something in Erik's gut told him that was not the case. A part of him was still angry that Alexi would not explain the entire plan as well. But as he sat silently for a few minutes, he realized that offering to take the same potion was about as trustworthy an offering as he could imagine. 

“I am not a kind man, Alexi. Some call me a soldier, some call me a freedom fighter, but most consider me a murderer and a terrorist. I have no love for slave owners, and I have expressed little besides hatred for you in the three days that I have been here. I would hardly call it low-risk to put your mind at my mercy, if that is truly what you are doing. 

Let me verify if that potion is doing what you say. If that potion truly caused you to feel what I do, then you should be able to answer this. You could have said I hated you and that I was angry without that. I have not exactly kept it a secret. But what else do you feel from me? Something that I have not already mentioned, some of which is even more powerful than my hatred of you for kidnapping me.” Erik's calculating gray eyes seemed to bore into Alexi's, trying to find some form of deception. But he could find nothing. Either Alexi Vandros was the most skillful liar on the planet … or perhaps he was in fact telling the truth.

There was another, equally important, point that came to Erik as well. Perhaps if he was wrong about the potion being ineffective on humans, then he was wrong about other points as well. 

“Also, you keep talking about how this is a 'pure-form', an original purpose, how this potion won't destroy us. If it doesn't break a person's will, then what does it do after the seven doses?” he finally asked. He had to know everything before he took this plunge. That couldn't possibly be too much to ask, considering it had not been long since he was so resistant to the idea that he would have died first. He had to be absolutely sure this was not a trick... but on the other hand, at some point, some terrifying point, he would have to trust that Alexi was telling the truth. At some point, he would have to take that leap of faith. All he could really do was try and make that leap as short as possible.