Original sentence: Ultimately, Freeman uses the co-operation of surviving scientists and security officers to work his way to the mysterious "Lambda Complex" of Black Mesa (signified with a "ʎ" symbol), where a team of survivors teleport him to the alien world Xen, where he must kill the Nihilanth, the creature keeping Xen's side of the dimensional rift open
Edited sentence: Ultimately, Freeman uses the co-operation of surviving scientists and security officers to work his way to the mysterious "Lambda Complex"(with it's famous "ʎ" sign) of Black Mesa, where a team of survivors teleport him to the alien world Xen, where he must kill the Nihilanth, the creature keeping Xen's side of the dimensional rift open