The Great Defender (Barriurgy)

Using your Shield as a spell focus, you project a dome-shaped barrier over your surrounding area that rapidly expands up to 5 miles in all directions, harmlessly passing through creatures and objects until it reaches its' boundary, where it solidifies. While you continue to channel, the barrier prevents passage in or out of the area. The shield has 1,000*STR mod HP, and is resistant to your choice of Magical or Physical damage. If you stop channeling, the barrier loses 500 HP per minute.

Allies inside of your shield gain your STR modifier as AC and Temp HP, refreshing at the start of each of their turns.