The White Deer are part of a World Change involving and The name of the world change is Overhunting, when the White Deer start to disappear you can capture the starving wolves luring them on magic wolf traps and delivering them to npc Benevola near to Ab'dendriel, that will make White Deer start to appear again.
Killing a White Deer can make she become a desperate White Deer or an Enraged White Deer, killing 400 make you get achievement 'Deer Hunt'.
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