Summon eruda devtool when you cast the spell.

summonEruda.js

;(function () {
  var step = 0
  function load (url, callback) {
    var script = document.createElement('script');
    script.src = url;
    script.onload = callback;
    document.body.appendChild(script);
  }
  function summonEruda (e) {
    if (e.target.dataset && e.target.dataset.summonEruda) {
      step++

      if (step >= 8) {
        load('//cdn.jsdelivr.net/npm/eruda', function () {
          eruda.init()
          load('//cdn.jsdelivr.net/npm/eruda-dom', function () {
            eruda.add(erudaDom);
          })
        })
        document.body.removeEventListener('click', summonEruda)
      }
    }
  }

  document.body.addEventListener('click', summonEruda)
})()

The repo of eruda devtool: https://github.com/liriliri/eruda
The spell: add attribute data-summon-eruda="true" to any element, then click it for more than 8 times.
minified:

!function(){var d=0;function t(e,n){var d=document.createElement("script");d.src=e,d.onload=n,document.body.appendChild(d)}document.body.addEventListener("click",function e(n){n.target.dataset&&n.target.dataset.summonEruda&&8<=++d&&(t("//cdn.jsdelivr.net/npm/eruda",function(){eruda.init(),t("//cdn.jsdelivr.net/npm/eruda-dom",function(){eruda.add(erudaDom)})}),document.body.removeEventListener("click",e))})}();