Only wanted criminals could be killed without any repercussions of any sort. What happened yesterday was because they had been given the order to kill. If he was found out to have killed his fellow cultivator, he would have been fined so hard that his heart could have burst open.
After circling around and making sure no one else was following him, Grey went to the same shop where he bought the poisonous herbs before. His heart clutched when he spent another twenty spirit stones. But because it affected his overall power, he bit had no choice to swallow the pill.
After refining a new batch of poison, Grey also refined some medicinal to sell. He didn't want it to be suspicious that he bought certain herbs but didn't make any pills. Most of the materials needed to refine pills are the same ones he used to make poison anyway.
