Ты see L'Arachel a few times in the game prior to becoming an avialible unit including trying to get to one country but goes the wrong way and ends up in another.
SPOILER ALERT
It is revealed that L'Arachel is not a traveller as first was thought but actually the princess of the theocracy of rausten. L'Arachel can get married with some other units in their endings and becomes queen.
L'Arachel starts as a low level troubador. not desirable for this stage in the game tower skirmishes are recommended so when she finnaly gets the chance to promote l'Arachel becomes a very helpful unit.