When I had the time, I was spawning Ry'thes several times a day. First I got a group of 3 so we could all run solo and invite each other to the spawns (= 3x the spawns) then I only stay until first bat wave (he spawns later sometimes but much higher probability on first "feast on their flesh" wave for me). He shows up top left corner in a purple piller of light. If he's not there, exit to map and repeat over and over as fast as you can. I never saw the axes drop. Ry'thes is rare and the axes are insanely rare. Spawn farm teams also work well for farming Moontear relics from Mad Scientist, orange ghosts at Halloween, and all other rare spawn incidents in game. Good luck.