Place the following runes in the spell block and activate them as normal:
+---------+---------+ | / | |\ / | | / | | \/ | | ( | | | | \ | | /\ | | \ | |/ \ | +---------+---------+
Your party should now be invincible, while still able to build up their stats.
In Loki's shrine use the empty bottle on the front to rise to a rune, Urgha uses the rune spell to get invulnerability.