D2 Helper is a free iPhone app developed by Luca Naterop. It falls under the category of Utilities & Tools and aims to assist Diablo II players in optimizing their gameplay experience. With D2 Helper, players can conveniently save the runes they own and easily access information on runewords they can create.

The app also allows users to keep track of their favorite runewords, ensuring quick reference during gameplay. Additionally, D2 Helper provides valuable insights on where to find specific runes, helping players in their quest to collect all the necessary materials.

Furthermore, D2 Helper offers a feature for players to track their Holy Grail data, enabling them to monitor their progress and achievements. Finally, the app includes a note-taking functionality for users to jot down important information about their mule characters.

Overall, D2 Helper serves as a valuable companion app for Diablo II players, offering convenience and organization in their quest to conquer the game.