This basically an enhancement on skills for each class. Equipping a certain equipment or a set of equipment will add additional effects and animations to certain skills of your class. For example, by equipping the "Ring of the Pyromancer" you will be able to convert your "Overload" skill to toss balls of fire that explodes and burns on impact instead of lightening balls.

With a set equipment you can summon different creatures instead of just a clannfear or twilight (e.g flame anoatch, deadric prince, phoenix, giant spider, etc etc) each with their unique skills and abilities.

There a probably numerous other skill modification (even if they are for vanity) for difference classes. This will allow a much more variety in building the perfect and efficient character.

Look forward to your responses

PS: Wondering though, should there be ultimates for weapons skill lines?