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="Friar_Set_Bonus" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1471" ns="10" title="Template:Baron Set Bonus" />
      <page pageid="1457" ns="10" title="Template:Bishop Set Bonus" />
      <page pageid="1473" ns="10" title="Template:Bloodletter Set Bonus" />
      <page pageid="946" ns="10" title="Template:Bosses" />
      <page pageid="944" ns="10" title="Template:Champions" />
      <page pageid="1463" ns="10" title="Template:Chancellor Set Bonus" />
      <page pageid="1889" ns="10" title="Template:Crusader Set Bonus" />
      <page pageid="1472" ns="10" title="Template:Daimyo Set Bonus" />
      <page pageid="1468" ns="10" title="Template:Duke Set Bonus" />
      <page pageid="1459" ns="10" title="Template:Emissary Set Bonus" />
    </pages>
  </query>
</api>