Jared Leto's mysterious Mars Island retreat promised fans a once-in-a-lifetime opportunity to spend time with the Thirty Seconds to Mars frontman. The band invited fans, who call themselves the Echelon, to the event held on Obonjan, a private island off the coast of Croatia. The luxury getaway was an immersive alcohol-free three-day retreat, which was said to have cost over $6,499 (£4.8K) to attend. It included accommodation, workshops, performances and group activities designed around creativity, self-expression and connection. Attendees were said to have swam, sunbathed, walked on the beach and engaged in yoga, all while celebrating…