In the beginning of the game, Warchasers, under the custom games tab, you select a character and that character should be designated as a Hero Character, thus being able to access an inventory with six slots (like in the game) and be able to pick up magical tomes. However, currently, the game doesn’t allow the player to do either of those things. Please fix.
Sorry this is 8 days late, but this was sometimes a bug in the original game, too.
You can fix it yourself with Hero Editor. Load up the map, find the hero on the left pane in the unit editor, go to abilities, and add “inventory (hero)” to them, then save.
It will save as a different map, so make sure you pick the right one in the custom games tabs.