Killings
It was the first killing committed after Emery from the Twilight Fang. And with the innate connection linking their minds to one another, he could clearly sense their thoughts and emotions during and at the end of the deed.
There were no fluctuations in Morgana's emotions, the red-haired half-blood was straightforward, following the orders without question. It was evident she had no fear or aversion to taking a life. Yoro surprisingly reacted similarly to her and, coupled with his grudge, a feeling of satisfaction coursed through him.
As for Andrei and Tatyana, even though they deeply resented the Corvin clan for the many things they had gone through, Emery could feel some discomfort and uneasiness from both of them. Clearly, they were still not used to killing and needed time.
Emery himself found no reluctance in such an act. It was necessary for them to cover up their tracks. Being their Alpha, Emery's justification helped the two quickly get over the matter.