The character was an online/Battle.net character (cannot be transferred).
For the truly curious, "patching" often involves manual hex editing. The .d2s file uses a byte order.
If you are currently trying to fix a broken character file, let me know: What the character was created in? diablo 2 lod character save files patched
This article provides the definitive deep dive into patched save files, compatibility, editing, and troubleshooting.
Characters were stored directly in the game’s install folder. Default Path: C:\Program Files (x86)\Diablo II\Save . 2. Identifying File Types The character was an online/Battle
Are you using any like PlugY, Median XL, or a Hero Editor?
If you don’t want to edit your own save, you might search for pre-made downloads. These are usually: If you are currently trying to fix a
Find your 1.14d .d2s files (usually C:\Users\[Username]\Saved Games\Diablo II\ ).