Bandos page 4

Bandos page 4 can be found as a reward from all levels of Treasure Trails.

The page can then be added to a damaged god book purchased from Jossik for 5,000 coins. There are 4 pages in total.

Once all 4 pages are added to the book it becomes a book of war, which you can then equip in the shield slot, or to preach from.