Placer une section grid à margin-top: 100%

.grid {
  position: relative;
  display: grid;
  grid-gap: 1.5rem;
  grid-template-columns: repeat(12, 1fr);
  height: 100%;
  margin-top: 100%;
}

.item {
  padding: 1.5rem;
  background-color: coral;
}

.text-content {
  grid-column: 1 / 9;
}

.illustration {
  position: absolute;
  grid-column: span 4 / -1;
  grid-row: 1 / 3;
  left: 0; 
  top: 0;
  right: 0;
  bottom: 0;
}

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							<h2>BOLO</h2>
							<blockquote><p>You have just dined, and however scrupulously the slaughterhouse is concealed in the graceful distance of miles, there is complicity.</p><cite>Ralph Waldo Emerson</cite></blockquote>
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<video autoplay loop muted="" playsinline="">
    <source src="/media/cc0-videos/flower.webm"
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    <source src="./videos/Emeline Fougeray.mp4"
            type="video/mp4">
</video></div>		<h2>Regula aurea.</h2>
							<blockquote><p>Until he extends the circle of his compassion to all living things, man will not himself find peace.</p><cite>Albert Schweitzer</cite></blockquote>
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							<h2>Dum spiro, spero.</h2>
							<blockquote><p>Thousands of people who say they 'love' animals sit down once or twice a day to enjoy the flesh of creatures who have been utterly deprived of everything that could make their lives worth living and who endured the awful suffering and the terror of the abattoirs.</p><cite>Dame Jane Morris Goodall</cite></blockquote>
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							<h2>Donna nobis pacem.</h2>
							<blockquote><p>The human body has no more need for cows' milk than it does for dogs' milk, horses' milk, or giraffes' milk.</p><cite>Michael Klaper M.D.</cite></blockquote>
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							<h2>Acta Non Verba.</h2>
							<blockquote><p>I think if you want to eat more meat you should kill it yourself and eat it raw so that you are not blinded by the hypocrisy of having it processed for you.</p><cite>Margi Clarke</cite></blockquote>
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				  <section class="grid">
    <h1 class="item text-content">Titre
    Titre
    Titre</h1>
    <p class="item text-content">Texte</p>
    <div class="item illustration">Illus.</div>
  </section>