: Don't you mean Murgen, rather than Rabican? Rabican was
: the best swordsman and physical fighter of the Nine,
: but Murgen was the finest mage amoung them.
GURPS speculates that "Alric probably wasn't the most magically skilled of the Nine - perhaps Murgen claims that description - [...]" but all we know of the latter is that he could argue with a grove of trees, and that he died when the Tain was reduced to the Shard.
The GURPS entry for Murgen is also reproduced below for anyone who doesn't have the book:
"Murgen was a particularly skilled sorceror, with a knowledge of the Gate college and extraplanar affairs unmatched by any of his colleagues. He also was a polished diplomat. He died in forcing an exit from the Tain[....]"
My early efforts to copy certain GURPS quotes for people to read stopped some time ago, but the above should be enough to see that there is nothing to prove he was the finest among the Nine.
-Welly