Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/tools/js/smartComponents/BoxBackground/BoxBackground.tsx

@@ -0,0 +1,26 @@
+import React from "react";
+
+import { CharacterTheme } from "@dndbeyond/character-rules-engine/es";
+
+interface Props {
+  StyleComponent: React.ComponentType<any>;
+  theme: CharacterTheme;
+  className: string;
+}
+export default class BoxBackground extends React.PureComponent<Props> {
+  static defaultProps = {
+    className: "",
+  };
+
+  render() {
+    const { StyleComponent, theme, className } = this.props;
+
+    let classNames: Array<string> = ["ddbc-box-background", className];
+
+    return (
+      <div className={classNames.join(" ")}>
+        <StyleComponent theme={theme} />
+      </div>
+    );
+  }
+}