How To Open.one Files

Yesterday I was struggling to find a way to enable ladder-only runewords on single player with the newer versions. Because my system does not cooperate with older versions of D2, I was especially motivated to get it working for 1.14. Ladder only runewords in single player. Just playing single player. Wanna make some runewords like Insight, but you can't do that since it's single player. Why is that so? Ladder-only runewords should be available in Single Player. I can try to play it on Multi and then just make a private one, but lagg and stuff, different maps everytime, etc.