It kind of looks like a little book. It's a rectangle with dashes on the side that represent the spirals of a notebook. There's a cross right on the front. Like the red cross. Or a Templar shield.
This Health Book icon is made in flat color style
. This format was developed by Icons8 designer team and became immensely popular for use in web and mobile applications. Feel free to download this icon in PNG format for free, or unlock other formats for $5. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 6,200 icons, all in the same style and quality.