Eilistraee's Song is a mod that expands the plot of Eilistraee - a deity of the drow who rebelled against Lolth the Spider Queen. Eilistraee is actually mentioned in the original BG2:SoA by Solaufein after we decide to let him go, but the players were never allowed to learn the full tale. This mods adds content for players who decided to spare Solaufein's life and let him escape. It means that your decision in the Underdark has actual consequences later in the game. I think it's a pity that in the original BG2 your decisions in Ust Natha don't really matter in the later chapters. When Solaufein finds you after you've escaped Ust Natha, he tells you how grateful he is. Eye for an eye, and friendly arm for a friendly arm - he tells you about a new location, where you can ask for help in getting your soul back. The mod includes 6 new areas, 21 new items (2 of which are available through Cromwell) and obviously some new quests - it's up to you if you want to complete them or focus on the main quests and getting your soul back. In the new areas, you may hear new music themes.
Also, a new kit becomes available after completing one of the minor quests, although there are some requirements (female, cleric base class, single class, kitless, non-evil alignment, elf or half-elf).
As with any other WeiDU mod, unzip the archive to your Baldur's Gate 2 (EE) directory and run Setup-Eilistraee.exe. The mod is compatible with Solaufein NPC (both Weimer's and Jastey's).
GAMES: BG2, BGT, BG2EE, EET