Spellbreaker must have been the inspiration for games like Mulldoon Legacy, Lydia's Heart, Jigsaw, and other intensely long puzzle fests (I feel like Curses! is slightly easier). This is Infocom's last game of the Enchanter trilogy, which follows the Zork Trilogy.
This game is incredibly long and difficult. I played to about 150 points out of 600 before turning to a walkthrough (eristic's), and most of those points I got because I had played Balances by Graham Nelson, which copied many items from Spellbreaker (to show that Inform could achieve the same results). The game is purposely murderously hard; I suggest that everyone use a walkthrough after reaching a predetermined number of points.
Magic is failing, and you must chase a mysterious figure to learn why. The game is pretty disjointed, but purposely so, much like Jigsaw, where you enter and exit various areas miraculously. It has a very different feel from Sorcerer, and especially from Enchanter, which was very easy to map and simple in its presentation.
Many people have talked about the time travel puzzle in Sorcerer, which I enjoyed, but felt a little down because there was so much hype. Unfortunately, I am now hyping the last big puzzle of Spellbreaker to you. What a puzzle; to me, it was great because it completely ties in with the game's theme of loss and ending. It is a puzzle integrated with the plot.
As a final note, I should really emphasize that this is a LONG game, 2 or 3 times as long as any other Zork or Enchanter game. When using a walkthrough, I finished each of those games in a total recorded time (not counting my numerous restarts) of about 16 minutes; this game, including several restarts to shave off the starting time, took 1 hour and 22 minutes.
I played this game on iOS's Lost Treasures of Infocom.