Dont know, I've never been there, but I guess there should some insurance you pay when you join to cover that expenses. I've tried to find information regarding injuries in the Wolin Festival (using google translator since the information is in Polish) and the only thing I could find was regarding a single injury that was not even that serious! But that doesnt seem right, in the Medieval Armoured Combat League (Battle of the Nations) they have better armour, strict rules (like no thrusting attacks), battles are smaller (5x5 and 21x21) and much more organized and yet they talk about injuries like broken bones (more than expectable in such a violent sport). In the other hand, the Wolin festival seem much more chaotic and I could find almost nothing talking about that (but again, I don't read polish).
Again, I'm not sure, In the BotN group battles you are out only once you hit the ground (so wrestling and tackles are usualy more effective than sword attacks), but in the Wolin it looks like they drop after being hit by weapons, maybe its like Airsoft where you have to be honest and declare yourself dead, and the observers are there to see if people follow that rule (and to prevent anyone dying for real). Still it must suck to play dead with that many people stomping around XD
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