Q: Will I need internet access to use D&D Insider
Answer: The D&D game table and the character builder are windows applications driven by a 3D-engine (DirectX based).
The character sheet, dungeon builder and encounter builder will be standard windows application.
You will indeed need to access the internet and be a D&DI subscriber to use these applications to their fullest potential.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.