A month went by since Erik and June killed Howell. In this time frame, Erik took Howell's identity.
Before killing Howell, Erik realized he had little time to complete his revenge against these guys.
Noah was still organizing the attack on Fasard to free his father, and the clone could call him at any moment.
For that reason, he came up with a simple idea to kill as many Crystal Cross Gang members in the shortest time possible.
It was easy, really. He simply needed to take Howell's identity and call everyone back.
A meeting was the excuse he needed to make that happen.
It would only take one day to kill everyone, but of course, he needed to give them time to arrange the trip, hence why he gave the deadline in a month.
In the meantime, Erik spent all the time he had available to study Howell's papers.
He learned a lot of stuff. For example, most of the guys that attacked him during his outing with the Red Palace died.