The incantation time of the Enchanter and Trance abilities is longer than the Boon/Affinity spells and the effect is both more powerful and shorter in duration, however having all four party members' weapons enchanted accounts for a great deal of fast damage, and better assurance of useful debilitations. It also ensures the Mystic Knight has the element they need to modify spells like Ruinous Sigil and Great Cannon in case pawns do not have the correct elemental affinity or are otherwise occupied in heavy battle.
Use the 'Come!' command to make sure all your pawns congregate and receive the effect.
Releasing this skill prior to fully charging the second bar casts Ice Enchanter, allowing the player to use either skill as the situation demands.