Elephant is an alternative theme for the main Mastodon web interface.
Unlike Elk, Elephant is done all with CSS theming, and provides an interface similar to what you might find from legacy Birdsites. The code for Elephant is also known as Bird UI, and is maintained by Roni Laukkarinen. It is available on GitHub.
To enable Elephant on your vmst.io account, visit Preferences > Appearance > Site Theme > Elephant.
This will work with the default single-column or Advanced multi-column layout options. There are also High Contrast and Light color theme options available.
To disable Elephant, simply select one of the default Mastodon themes from the same control panel option.