#mallorean

Pheris Erondites and Eugenides, from Megan Whalen Turner's Queen's Thief series

Mags, from Mercedes Lackey's Valdemar series

Diana Hyde, from Theodora Goss' Extraordinary Adventures of the Athena Club series

Silk and Velvet, from David and Leigh Eddings' Belgariad and Mallorean pentologies

the goddess Aphrael, from David and Leigh Eddings' Elenium and Tamuli trilogies

In the Belgariad, Silk has several super important moments, the biggest one obviously being killing Brill. Granted, in the first series not everyone's role is super obvious the way it is in the second series (I could be blanking, but I don't recall Hettar having a big moment to himself). But in the Malloreon, every companion gets a really emphasized Task that's the reason they had to come along at all, in addition to all the other generally helpful stuff they do. This is even discussed in character, such as when Ce'Nadra is convinced she's going to be the one to die because she thinks she didn't have a Task.

For the sake of comparison, I'll run through the companions and their Most Important Task:

Garion - Child of Light/Godslayer - choose successor

Belgarath - Beloved and Eternal - find and follow the secrets

Polgara - (no prophecy name afaik) - banish Chabat's demon

Durnik - Man With Two Lives - banish Nahaz

Poldara - Woman Who Watches - fight Zandramas

Eriond - Bearer of the Orb - become a God

Ce'Nedra - Queen of the World - let Zandramas know about Korim

Liselle - Huntress - kill Harakan (with Zith)

Sadi - Man Who Is No Man - kill Naradas

Zakath - Empty One - convert Mallorea (post-Choice)

Toth - Silent Man - confront dragon (argument could be made for his "betrayal" on Verkat as well)

Remember that Beldin isn't named in the prophecy, he's the plus-one they got to bring along since Zandramas brought more help than was legit (I'd guess the dragon-demon hybrid tipped the scales).

By contrast, the times when Silk is in focus in the story mostly have to do with people connected to him. Liselle is the one who realizes Urgit is his half-brother. Silk's factors in various cities give them important info. They run into a bunch of his hired mercs at one point. But Silk himself doesn't have a Thing He Does that's particularly useful.

On top of that, a lot of the roles he played in the Belgariad can be played by other teammates in the Mallorean. Velvet is young but clearly talented. Sadi is extremely good at what he does and is the one in charge of leading the party through Cthol Murgos. Beldin is exceptionally skilled at deception and he does the majority of leading everyone around Mallorea. And Durnik, in a memorable scene, shows that he's picked up enough from Silk to be quite a good backup spy.