May 4, 2011: Flux
As of the April 29th update, the Global PvP effect, Flux, was added. With this, there has been implemented a monthly cycle of passive, environmental effects which effect all players in any PvP Arena. As stated in the Developer Notes which came out in parallel with this update,
"The introduction of Flux is a compelling tool to help us keep our competitive formats dynamic, while allowing us to further balance the game. Because slight shifts in the meta are expected from Flux to Flux, it allows us to better target overly problematic builds. If powerful builds can thrive in environments that are not suited to them, we can review the skills to bring them more into line. We want to encourage gameplay where the team that wins does so because they've played more skillfully.".
Currently, the effect is called Unyielding Spirit. This effects boosts damage dealt by a player, by 1% for every 2 points of Death Penalty incurred. While this Flux is not conducive to any certain build, this can notably influence team formats such as GvG, where base pushes can be thwarted by teams resurrecting after a wipe, or HA, in formats such as King of the Hill.