<svg width='0' height='0'>
  <defs>
    <clipPath id='cp'>
      <path d='M285,150 L83,33 L83,267 
               L285,150
               L258,150 L96,244 L96,56
               L258,150z'/>
    </clipPath>
  </defs>
</svg>

<div class='clip-me'></div>

@import "compass/css3";

.clip-me {
  width: 300px; height: 300px;
  background: #222;
  clip-path: url(#cp);
}