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 atcontinue="Badab_Marines_Errant_Infobox" />
  </query-continue>
  <query>
    <alltransclusions>
      <t ns="10" title="Template:Badab Astral Claws Infobox" />
      <t ns="10" title="Template:Badab Carcharodons Infobox" />
      <t ns="10" title="Template:Badab Executioners Infobox" />
      <t ns="10" title="Template:Badab Exorcists Infobox" />
      <t ns="10" title="Template:Badab Fire Angels Infobox" />
      <t ns="10" title="Template:Badab Firehawks Infobox" />
      <t ns="10" title="Template:Badab Howling Griffons Infobox" />
      <t ns="10" title="Template:Badab Influence" />
      <t ns="10" title="Template:Badab Lamenters Infobox" />
      <t ns="10" title="Template:Badab Mantis Warriors Infobox" />
    </alltransclusions>
  </query>
</api>