SVG Graphic for lower right page turning, designed carefully by hand, keeping the SVG code as simple as possible

page-flip-corner.svg

<svg width="100" height="100" xmlns="http://www.w3.org/2000/svg">
    <defs>
        <linearGradient id="toblack" x1="6%" y1="6%" x2="80%" y2="80%">
            <stop offset="0%" style="stop-color:rgb(0,0,0);stop-opacity:0;"/>
            <stop offset="100%" style="stop-color:rgb(0,0,0);stop-opacity:1;"/>
        </linearGradient>
        <linearGradient id="shadow" x1="45%" y1="45%" x2="70%" y2="70%">
            <stop offset="0%" style="stop-color:rgb(0,0,0);stop-opacity:1;"/>
            <stop offset="10%" style="stop-color:rgb(0,0,0);stop-opacity:.9;"/>
            <stop offset="100%" style="stop-color:rgb(0,0,0);stop-opacity:0;"/>
        </linearGradient>
        <mask id="page-corner-curves">
            <rect width="100%" height="100%" fill="white"/>
            <path d="M 100 0 C 100 20 25 20 10 10 C 20 25 20 100 0 100 L 0 0 Z" fill="black" stroke="white"/>
        </mask>
        <mask id="complete-page-corner-with-curves">
            <rect width="100%" height="100%" fill="white"/>
            <path d="M 100 0 C 100 20 25 20 10 10 C 20 25 20 100 0 100 L 0 0 Z" fill="black" stroke="white"/>
            <path d="M 98 4 L 10 10 L 4 98 Z" fill="black"/>
        </mask>
    </defs>

    <polygon points="100 0 100 100 0 100" fill="url(#shadow)" mask="url(#complete-page-corner-with-curves)"/>
    <path d="M 98 4 L 10 10 L 4 98 Z" fill="url(#toblack)" mask="url(#page-corner-curves)"/>
</svg>