A new high-difficulty setting featuring account-wide rewards and restricted matchmaking.
To understand the necessity of v1.1.0a, it's important to look at the massive additions made just days prior in the Wayfinder Wiki's v1.1.0 overview : Wayfinder.Update.v1.1.0a-RUNE.rar
Your old saves (from previous RUNE releases) carry over, but the Echoes update will convert them automatically on first launch. To be safe: Wayfinder.Update.v1.1.0a-RUNE.rar