I've been an avid player of Avalon for over eight years now and in that time I've ridden the rollercoaster of highs and lows and passions and emotions hundreds of times. There's something keenly addictive about it that draws you in again and again and again and it's by far the best MUD / online RPG type game I've ever come across.
PVP and warfare are my two big passions in the game, the combat is fast paced, detailed and very challenging with so many different spells and abilities available (I play a Mage, light magic and fireballs and enchantments), while the warfare is all about strategy and battlefield terrain and leading your soldiers to victory. I think the best thing about it is that your actions have consequences on the world - something other games tend to offer artificially whereas Avalon it's do or die.