Sea of Stars

A "lock" in this regard is a series of symbols that will appear over an enemy's head as they power up a big attack which will correspond to a type of attack. This could be your normal attack (such as a sword for a slashing attack with Zale) or a magical symbol (such as a moon for Valere). You will need to use those types of attacks enough times to interrupt the channeling of the enemy's attack, thus "breaking their lock" and preventing the attack. It will usually take two characters and most attacks take two turns to charge, so this isn't very difficult - and often it only takes two of the same symbol so a perfectly timed attack from one character can take care of it. You should get this extremely early on in this game.

Note: If you absorb the live mana that drops when you hit enemies, this will imbue your normal attack with the element of your magical attack, allowing you to break both types of locks at the same time. If you need a slashing and solar attack, you can do both with Zale in one attack, for instance. However, this only works on the first attack, so a perfectly timed attack with Zale will always be two slashing locks and one solar lock - even if you absorbed two balls of live mana.