Kalani is correct about the APL. We design the first three to be optimized for an APL of 11th, 12th, & 13th respectively. The follow-up trilogy will focus on 14th, 15th, & 16th levels. That said, like other DDAL adventures, there is guidance for scaling the encounters. The combat tends to be on the easier side of the difficulty scale for this trilogy, so a DM should be prepared to ramp things up for more of a challenge.