Rift's annual celebration, Carnival of the Ascended, will begin on April 14, 2016, as part of v3.6 update. Special events will be taking place including a Carnival Instant Adventure, new Artifact sets, a new story raid rifts, daily quests and much more.
Carnival Instant Adventure: Boglings are running wild and terrorizing the citizens of Tempest Bay. Taking inspiration from some of the Ascended’s greatest enemies, many of these Boglings present a greater challenge than their humble origins might suggest. Battle it out and prevent their rebellion, lest Tempest Bay fall to these malicious malingerers.
You can read more details on the Rift site.