Sets released: Visions, Fifth Edition, Portal, Weatherlight, Tempest

Major stuff:

   - Fifth Edition tightened up the timing rules even further, bringing in
   phase abilities, phase costs, pre-series and all sorts of long-forgotten
   concepts.
   - The card templating changed again; abilities with non-mana and
   non-tap costs used to be phrased '{0}: <other cost> to <effect>'.
   This was changed to the more modern '<other cost>: <effect>' to keep
   all the costs on the same side of the colon.
   - Fifth Edition saw the introduction of mana source cards.
   - Fifth Edition forced players to play interrupt cards that targeted
   a permanent using the timing rules for instant cards.
   - Fifth Edition removed an older rule about 'pumping' that allowed
   a player to announce and pay for multiple activations of an effect
   at once.
   - April 1997 introduced the modern 'Paris mulligan' rule; previously
   a mulligan required either all land or no land in the hand and could
   be taken only once, now the mulligan can be taken as many times as
   desired with any hand, but reduces starting hand size by one each time
   the mulligan is taken.

Trivia:

   Portal was a vastly simplified version of the game, using just
   creatures, sorceries and lands.
   Iconic creatures Serra Angel and Sengir Vampire were dropped from
   the base set for Fifth Edition.