A description over on Xbox.com has laid bare details of Rise of the Tomb Raider's season pass. As it turns out this will include Endurance Mode, a new tomb, and a wave-based mode called Cold Darkness Awakened:
"The Season Pass for Rise of the Tomb Raider includes a range of content that will extend your single-player campaign, and also allow you to compete with friends. Three major releases will challenge you to survive the extreme conditions of Endurance Mode, explore a new tomb that houses an ancient terror in Baba Yaga: The Temple of the Witch, and combat waves of infected predators in Cold Darkness Awakened. In addition, a steady stream of outfits, weapons, and Expedition Cards beginning on Day 1 and continuing over four months will keep you customizing, expanding, and challenging your friends to new adventures."
Sounds like Square-Enix and Crystal Dynamics has quite a lot in store for those who plan on expanding their Rise of the Tomb Raider experience.