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>
    <duplicatefiles dfcontinue="0a0x_nightmask_1.3r1_icon1.jpg|0a0x_nightmask_1.4_icon1.jpg" />
    <allimages gaicontinue="0a0x_nightmask_v1.1.4_icon1.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2111" ns="6" title="File:0a0x nightmask 1.1 icon1.jpg">
        <duplicatefiles>
          <df name="0a0x_nightmask_1.2_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:42Z" />
          <df name="0a0x_nightmask_1.2r1_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:43Z" />
          <df name="0a0x_nightmask_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:43Z" />
        </duplicatefiles>
      </page>
      <page pageid="2597" ns="6" title="File:0a0x nightmask 1.1r2 icon1.jpg" />
      <page pageid="2112" ns="6" title="File:0a0x nightmask 1.2 icon1.jpg">
        <duplicatefiles>
          <df name="0a0x_nightmask_1.1_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:42Z" />
          <df name="0a0x_nightmask_1.2r1_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:43Z" />
          <df name="0a0x_nightmask_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:43Z" />
        </duplicatefiles>
      </page>
      <page pageid="2113" ns="6" title="File:0a0x nightmask 1.2r1 icon1.jpg">
        <duplicatefiles>
          <df name="0a0x_nightmask_1.1_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:42Z" />
          <df name="0a0x_nightmask_1.2_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:42Z" />
          <df name="0a0x_nightmask_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:04:43Z" />
        </duplicatefiles>
      </page>
      <page pageid="2598" ns="6" title="File:0a0x nightmask 1.3 icon1.jpg" />
      <page pageid="2467" ns="6" title="File:0a0x nightmask 1.3r1 icon1.jpg">
        <duplicatefiles>
          <df name="0a0x_nightmask_1.3r2_icon1.jpg" user="Destiny guide" timestamp="2014-07-25T07:36:15Z" />
        </duplicatefiles>
      </page>
      <page pageid="2468" ns="6" title="File:0a0x nightmask 1.3r2 icon1.jpg" />
      <page pageid="2599" ns="6" title="File:0a0x nightmask 1.3r4 icon1.jpg" />
      <page pageid="2469" ns="6" title="File:0a0x nightmask 1.4 icon1.jpg" />
      <page pageid="2114" ns="6" title="File:0a0x nightmask icon1.jpg" />
    </pages>
  </query>
</api>