From Halopedia, the Halo wiki
Lancer Squad is a squad of UNSC Marines who fought in the Installation 07 conflict. Around the time John-117 arrived on the fragmented section of Zeta Halo, Banished forces captured Lancer Squad and tied them to a restraint generator. The Chief's AI companion, The Weapon, picked up Lancer's distress call, prompting the Spartan to aid the marines.
In Halo Infinite, Lancer Squad is found in the "Connections" section of the campaign. Answering their distress call earns the player 30 Valor points. This valor is awarded even if all members of Lancer Squad are killed.
List of appearances