Era of Peace

At the beginning of your upkeep, gain life equal
to the number of nonland white permanents you control.
All creatures lose haste and trample, and if they are attacking they get -2/-0.
Whenever a source deals damage to a player, that source deals half that damage instead, rounded up.
"No wars had been fought in centuries, and the sounds of battle were silenced."
-The Scroll of Eras