Elric has several magic systems.
1. Runes
These replicate small spells sometimes found in the stories: localised magical effects that have certain similarities to Common Magic but actually work very differently and reflect the Elric saga's use of runes.
2. Summonings
Elric doesn't use the RQII sorcery. In its place one summons and controls elementals and demons to do your bidding. I wouldn't say its more powerful than core RQII sorcery (although it IS powerful - a 5 Magic point demon of combat is a bloody nasty thing to come up against) - but it is very different and doesn't rely on spells as such. It can also be very dangerous to use. Summon a demon and fail to control it, and it might turn on you...
3. Dream Magic
This is specifically the ability to steal and manipulate dreams. You'll find dreamtheft in the story 'The Fortress of the Pearl'. It also incorporates a certain kind fo HeroQuesting, which you'll find in 'The Skrayling Tree'.
4. Spirit Magic
A refinement of the core Spirit Magic rules with some tweaks here and there, but essentially the same.
The Elric magic system is very closely modelled on the books. Pete and I designed it several years ago and combed every Elric story available to ensure we got the nature and balance right. I think we did.
The other thing to note is that cult membership grants gifts and compulsions which can also function as quasi-magical powers. Elric cults are far more reliant on these than Glorantha cults, and even non-magic users who are willing to pact their souls to a god can attain some quite extraordinary powers - again mirroring certain characters in the books.