How are you meant to kill the first shielded unit?

Solution 1:

I played some more, and with some more understanding of the game mechanics, this is not as daunting as it appears at first.

Firstly, damage dealt is the simple calculation of the attacker's attack stat minus the defender's defense stat. What makes this shielded unit so formidable is that his shield grants +3 defense, giving him a total of 9. That means, to deal more than 1 damage at a time, you need to have an attack stat of at least 11. Grind until your attack stat is high enough to be useful, or attack with magic (which isn't affected by defense), in order to prevail.

Another thing that helped out immensely was actually running away from the battle. By killing all the other enemies on the battlefield, then retreating, that allowed me to swarm this single enemy on my next visit to that battlefield, since he was the only enemy that remained.

Use the time between your retreat and your next attempt to grind at the first shrine. There are 2 enemies in there, and they respawn every time you visit the shrine proper or exit the dungeon. After 3 trips back and forth (12 quick battles), the shielded enemy in the main mission posed no difficulty at all, even without a mage.