PC-12 pilot reported a MAU-A (Master Avionics Unit- A) caused cascading failures which led to altitude and heading deviations. Pilot regained control of aircraft and landed at destination airport.

Narrative

On Day 0; we flew from ZZZ to ZZZ1. During the descent phase we experienced a very material avionics failure in our Pilatus PC-12. That series of cascading failures and the attention placed on troubleshooting the situation while also flying and navigating resulted in a deviation from the heading and altitude we were assigned. I estimate the deviation to be approximately 300 ft. and as much as one mile (we were initially vectored and then given direct to a fix). We communicated our avionics issues to ZZZ Approach and asked for greater flexibility in our navigation.The Controller acknowledged and appeared to understand our situation while also not adding to our workload.Failures that occurred (from the Crew Alerting System) include: Initial: Check DU 1+2; Check Pilot PFD; MAU A Fail; ASCB Fail; TAWS Fail; Flight Director Fail; Autopilot Fail; Yaw Damper FailFinal: APM 1 Fail; Check DU1+2; Check Pilot PFD; MAU A Fail; ASCB Fail; AFCS Fault; Takeoff Config; CFM 1 Fail; Aural Warning Fault; TAWS Fail; Flight Director Fail; Autopilot Fail; Yaw Damper FailInitially this left us flying by a 2x2 inch EFIS on the pilot side. The flight was also very turbulent and at a busy pre landing phase at the time of the failure.The combination of these items kept me very focused on the flying component of the situation. I leveraged my passenger by asking them to read checklists.That was positive; however they are less familiar with the PC-12 and the combination of the large number of failures/checklist choices and my focus/distraction prevented me from providing the most effective guidance as to which checklist to start with. We have since debriefed and practiced the situation again so we are better able to work together if a similar situation arises.We were able to configure the co-pilot's Primary Flight Display (PFD) to provide additional basic information and effectively remedy our altitude deviation very quickly (a minute or two) while the Controller switched us from heading to direct to a VOR so it's difficult to estimate how long we deviated laterally. Shortly following the failures (perhaps five minutes) we were able to locate the ZZZ1 visually and were cleared visual to the runway as is typical on an IFR flight. At that point we switched to Tower frequency and landed uneventfully.