The biggest change is that the game is now spawning event-related rifts at a much-increased rate, to the relief of frustrated players looking for a good death rift and finding none. The update also encourages players to stay in level-appropriate zones by not counting closed rifts for the player if the player is far above that zone's level.
Trion added several new items to the event merchant, including additional pets and death-themed accessories. It's now easier to purchase these items, as the game is handing out Otherworldly Sourcestone -- the currency for the event -- in increased amounts.
The notes also indicate that players will have better chances at big rewards as the River of Souls event progresses, which gives us something to look forward to in the next few weeks! You can read the full patch notes over on the RIFT forums.