Thad started the mountain build on a sub server February 11th, 2021. He since has moved the chunks over to a solo world so he could continue the build beyond the reset of the server it was originally on. This is why he has some unique feature in his world...basically a massive void beyond the chunks he downloaded from the server
While it's not hardcore, Thad has yet to die in this world, including the time it was on a server. He's on 100+ days of playtime with zero deaths.