Heavy Leather - Orc or Silver Weapon - more or at 280 stamina, and having at least 200 when the event with Makhor begins - defense at 4 - LEVEL 5 - special training for beast at cost of 150 stam.
If you have everything of this and still it doesn't work, it's a glitch probably. At the beginning I've tried to go where the ren'py folder is located and canceled all the save with the persistent file, and then canceled all the save in KoD folder.
Nope, 4 def is: 2 (with heavy leather armor) + 1 (buying training for defense at "training grounds") + 1 (completing training "Red God Arena")
Do the stamina training first to have more stamina and recover a little bit more of stamina everyday, than decide wich to do first between the dogde training and the defense training.
If you manage you're stamina well, you can complete all the trainings in the arena, the secret is never spar with orcs in the Red arena and starting the Red God Arena event from the first day by having 270 STAMINA