Planar Chaos uncommon. The design version of Shivan Meteor dealt 20 damage, fully double the previous printed damage record held by Urza???s Rage and Searing Wind. The decision was made to play around in the space between 10 and 20, saving the big two-oh for (perhaps) another day. And maybe, just maybe, somebody on the Development team had a soft spot for Autochthon Wurm.
