From D&D Wiki
Locking pages can be done to protect pages from the edits of non-admins. This is usually done for OGL pages, where we don't want anyone to edit them like normal pages (since the point is to preserve them in original form), reference pages which contain info on how to find published 1st party content that is not OGL and hence can not be hosted on D&D Wiki, and list pages as to prevent vandalism to site infrastructure.
Besides these reasons, homebrew pages can also be locked so that they can only be edited by admins for two other reasons: if there is an edit war or if a trustworthy user wishes for their complete page to be locked. In the case of an edit war, the page should only be temporarily locked as to prevent users from continually reverting each other's edits and/or so a discussion about the contentious issues can be held. If a user asks for their page to be admin locked, the page must be complete and not have any maintenance templates or other issues. See the completed pages category. Please ask an admin for help with locking your page by editing User talk:Admin, asking an admin on their talk page, or using other means.
If a page is being harmfully edited by anonymous users, you can request an admin to protect against unregistered users, allowing logged-in users to edit it, but preventing harmful spam or insistent edit warring. Pages that are semi-protected should not be locked indefinitely. Please report such requests to an admin, by editing User talk:Admin, by asking an admin on their talk page, or using another avenue.