You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="Infobox_Game|1386" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1384" ns="0" title="The Gray Knights" />
      <page pageid="1387" ns="0" title="Swords of Redemption" />
      <page pageid="1390" ns="0" title="Swords of Light" />
      <page pageid="1392" ns="0" title="Dirt City (game)" />
      <page pageid="1403" ns="0" title="Crescent Valley" />
      <page pageid="1547" ns="0" title="Blackbird Lake" />
      <page pageid="1666" ns="0" title="Ice Vein" />
      <page pageid="1777" ns="10" title="Template:Infobox" />
      <page pageid="1866" ns="10" title="Template:Redirect" />
      <page pageid="1989" ns="0" title="Teucri Lifewalkers" />
    </pages>
  </query>
</api>