Simple Sentences:
* The stars in the night sky were countless.
* He had countless opportunities to succeed, but he squandered them all.
* The internet offers countless resources for learning.
More Complex Sentences:
* Countless generations have walked these same paths before us, leaving behind a legacy of stories and traditions.
* Despite the countless challenges she faced, she persevered and achieved her dreams.
* The museum housed countless artifacts from ancient civilizations, each telling a unique tale of human history.
Figurative Language:
* The artist's imagination seemed to hold countless worlds, each one more fantastical than the last.
* His love for her was countless, overflowing with affection and devotion.
Note: "Countless" typically implies a large and uncountable number, so it's usually paired with a plural noun.
Let me know if you have any other questions!