Abaddon the despoiler's daemon blade is known as Drach'nyen, and was discovered below the crypts in the tower of silence on the world of Uralan duing the first black crusade. It is variously noted as having the ability to "tear reality apart".
Today, I wanted to quickly compare its abilities between the 2002 and 2007 codex editions.
In 2002, Drach'nyen was able to automatically penetrate any vehicle on hitting, gave Abaddon an extra attack, ignored armour and caused instant death.
In 2007, the new codex saw Drach'nyen give Abaddon an extra 1d6 attacks, and when combined with the Talon of Horus, allows re-rolls to wound and doubles his strength to 8. The downside is that Drach'nyen shares the bad bits of its counter-parts: a roll of a 1 on the 1d6 for the extra attacks means that the daemon blade is playing up and decides to inflict pain on Abaddon.
The change from a leadership test for mastery of the blade to a 1d6 test is severe: the chance of failure went from 3 in 36 (=0.083) to 1 in 6 (=0.167). I would very much like to see Abaddon not have to take this test: surely if anyone has mastery over chaos, it is Abaddon himself. I also think that the automatic penetration of vehicles was a good thing for a reality tearing blade to possess -- its loss is missed by old timers like myself!