PA28 pilot reported a spatial disorientation event when his safety pilot elected to climb into IFR conditions despite not being qualified. Pilot reported recovering from an undesired aircraft state at 800 AGL as they exited the cloud layer.

Narrative

Here is an accurate event description; written a few hours after the incident by me. XA:45 - Arrival to ZZZ AirportXA:47 - Entry/Exit of FBO; talked to Person A; Person B.XA:50-XB:00 - Sitting in my car; checking weather on possible routes. I unsure of where I was going.XB:05 - Walking to Aircraft. Begin Pre Flight Checks; refuel the aircraft.XB:15 - Call Person A; ask where my co-pilot is; and await his arrival. Pre Flight checks are done. The plane is airworthy and refueled. XB:35 - Person C Arrives; my co pilot. We check oil one more time; and we are intending on flying to ZZZ1; then to ZZZ2. We fill the oil up with one more quart; and settle into the aircraft. XB:40-XC:00 - Engine start; ATIS taken down; Pre Taxi Checks complete. Taxi to active runway; XXR. XC:01-XC:07 - Follow Run Up check list; hold short of Runway XXR.XC:08 - Takeoff.XC:09-XC:59 Flying from ZZZ; flying a North Heading. XD:00 PM - Person C states that we are going to fly through some clouds to avoid a thunderstorm; we are going to fly to ZZZ2 instead of ZZZ1. I ask if he is IFR certified; and he states that he is not.XD:01 PM - Person C has controls; and begins climbing through the incoming clouds. We fly through some small ones; and I begin to get nervous. He tells me its all good; and begins to fly deeper into the clouds.XD:02-XD:03 PM - Person C flies deeper into the clouds. He becomes disoriented. My eyes are on the altimeter; and Vertical Speed Indicator (VSI). All of a sudden; he begins to pitch down; and begins to roll left. I tell him he is pitching down; so he pitches up; and yanks on the yoke; causing the plane to climb for some seconds before nearly stalling; I did not hear the stall horn go off. My Ipad; phone; water bottle; as well as his ipad go flying throughout the cabin. A plastic oil jug flew to the front and hit my head. He then pitches down at a extreme rate; my eyes are still on the VSI as the arrow on the VSI starts rapidly turning left; passing the - 2000 foot per minute rate. I take control of the plane; my training kicks in; and I pull out of the dive. I pull the power and level off below the clouds at around 800 feet. We were at 2;500 ft two minutes before this. After this; he told me everything is alright; and that this was just a minor incident. I took control of the yoke and throttle and guided our nose to turn back south and head back to ZZZ. XD:04-XD:52 PM - Navigate back to ZZZ; safe landing; park; and tie down the aircraft. This event nearly took the lives of both the pilot in command and myself. We were flying at night to work on time building for our IFR requirements. When we landed; he turned to me; and asked if I was going to tell anyone; and I replied no. The first thing I did when I left the airport gates and entered my personal car was record flight information.