If you subscribed to the Google calendar, it's not possible to hide individual events, but there is a workaround. Open the events you do care about, click the three dots in the upper right corner, and select "Copy to (Name of one of your other calendars)". This will copy the event details into your personal calendar of choice. After that, you can unselect the MUD Anniversaries & Community Events calendar to hide it. (Alternatively, you can simply add individual events to your calendar.)