You can obtain netherite by summoning and killing a boss named Bajie. Here's how: https://wiki.ccnetmc.com/Slimefun/Runes

Except killing Bajie is extremely difficult and there are no guides on how to defeat either boss, not to mention how very little presence there is on the server that trying to get a corrupt rune on your own is a waste of time and gold.

1) You can always cheese bajie using slabs, trapdoors, or like so many other ways.
2) The wiki has complete info about bosses afaik
3) 36 Gold (324$ or 432$) for 1 netherite ain't a bad deal, you can always withdraw from bank instead of grinding
4) You can spawn as many bajie as you want in the 10s timeframe, just get gud.