0.5.5 Patch Notes - Forbidden Rites

The Forbidden Rites event league (Standard, Hardcore and Solo Self-Found). Headline changes:

Campaign Rituals: Ritual Effigy clusters appear twice per Act and once per Interlude; Tribute can be spent on Unique Items and party members earn their own Tribute.
Sacred Blooms are a Ritual reward that can add the Viridian Wildwood to a cluster of Maps on your Atlas; they can only be found in the Forbidden Rites league.
Trial of Chaos runs can be left and resumed, each room ends in a reward chest, and the rewards for completing a run are now only Currency and Soul Cores.
Expeditions (Runes of Aldur) are now a core Atlas mechanic, including in Standard; you can find them from Act 4 onwards.
17 new Soul Cores (13 Jiquani, 4 Atziri); Atmohua, Cholotl and Zantipi Soul Cores now convert 40% of requirements (was 20%).
Arbiter of Ash and Arbiter of Divinity swap their all-elemental resistances for a single resistance plus a vulnerability.

See the official forum thread for the complete notes.