There are a few versions of L'Arachel that appear as playable units in Fire Emblem Heroes. The regular version of L'Arachel appears as "L'Arachel: Princess of Light" in 3 and 4-star rarities. "L'Arachel: Seeker of Justice" is a younger version of her that appears as a 5-star. "L'Arachel: Harvest Princess" is another special 5-star variation of the character. The different versions are all obtainable and also appear in some chapters and paralogues. If you want to obtain the 5-star versions, keep an eye out for the special seasonal banners in which she appears.