Okay just about finishing up my re-read of the Dresden Files and just have a few quick questions/clarifications.
1. What is the difference between Carlos's entropy water magic and Entropomancy that the Fomor and other magic users use?
Carlos's magic is more of a thermodynamic Entropy:
Ramirez's spell was based on principles of entropy and water magic, and focused on disrupting, shattering, and dispersing any objects trying to pass through it, turning their own energy against them. Even magic must do business with physics, and Carlos couldn't simply make the energy the bullets carried go away. Instead, the spell reduced their force by shattering the bullets with their own momentum, breaking them into zillions of tiny pieces, spreading them out, so that their individual impact energy would be negligible.
Entropy Curses and the Fomor Entropy Magic are Bad Luck Spells, more along the lines of the Murphionic Hexes that inject additional chaos into a system until it breaks:
The fomor practice entropy magic. They make the antitechnology effect Dresden puts off look like mild sunspot activity. Modern systems are going to experience problems near him.”
2. I was reading the Dresden Files RPG Our World, I play it with friends, and it mentioned Molly Carpenter in Small Favor was trying to learn another element evocation aside from Spirit and Wind. Aside from the spirit shield at the beginning I do not recall any other element she tries to use unless I overlooked it or it is in another book?
There was no mention of it during SmF that Im aware of, any more than she showed the Sight or strong Thaumaturgy, as Our World mentions. By Changes she had all that "One Woman Rave" illusion magic, so Id suspect Fire as a component of Holomancy. It makes more sense for her to try than Earth or Water, given Harry is the one teaching her. For that matter, since Harry struggles with the weight of Earth Magic and Molly struggles with only Air, I wonder if she could use earth magic at all?
3. Lastly, do the winter or summer mantles give you the ability to do magic in general or only a certain kind of Fae magic? Molly and Harry can do things with magic that does not involve their mantles, and I was curious if Fix/Lloyd Slate or Maeve/Lily/Sarrisa could do magic as versatile as they could.
Best Explanation I can offer is that the Mantles offer you a Power Source. Anyone (with said mantle) can channel that power directly, and it manifests as it naturally does: as Fire and/or Ice. But those with their own skills with manipulate those energies (ie wizard talents) have more flexibility. Im a nerd, so in this context I think of the Mantle as a big car Battery: hand anyone a Car battery and they can use it to Weld, which is undeniably cool and useful. But a person who brings their own electrical/electronic system to the table can do a hell of a lot more with the energy in that battery.
And it's not just Mantles, the same is more or less true for lots of things. The Vampires (whites at least) can use their Hunger to Juice magic if they have the skills. All Denarian hosts get some basic powers and shapeshifting and whatnot, but if they take the time to learn magic they get hellfire-enhanced spells and such.