The cost reduction applies only to generic mana in the total cost of noncreature spells you cast
The set introduced role tokens, and has other great cards such as Stroke of Midnight, Blossoming Tortoise, Agatha's Soul Cauldron, and a cycle of strong virtues
So, you read Valduk and think, great, I just jam a bunch of equipment/auras on this and go to town! Well, thats not generally how it plays out
however, after you've grasped how they work, the primary mode is the co-op adventure
Beanstalk Giant Beanstalk Giants adventure, Fertile Footsteps, is a pretty good ramp spell
Remember that auras and equipment you attach to Alexios will stay attached when it changes controllers, and backgrounds like Popular Entertainer will still affect it, even when your opponents are declaring Alexios as an attacker