Personally, I'm not a fan of WoL. I'm in a Forgotten Realms game and the GM is currently in the process of running the Demonweb Pits module. We have high level characters (15-18), so he's adjusted the encounters accordingly. In any event, we've discovered two legacy weapons, one of which is the Black Bow. I have an archer character, so at first I was excited...until I realized just how much the personal cost was. I understand the intention of the writer of WoL was to make the weapons balanced, but by the time my character reaches 20th level, he would have to permanently sacrifice a total of 16 hit points, -3 to attack rolls, and a whopping -6 to all saving throws. All this for bow that is +4 with Drow Bane and a panoply of other abilities, but many of which are situational, limited, and/or not all that useful. The Black Bow's extra abilities just aren't anywhere near worth sacrificing 6 to all of his saves (something very important for character survival), much less the hit point and attack rolls penalties on top of it. While I love the idea of a legacy weapon which grows with the character, I don't think the attempt to balance the weapons was very well thought through and implemented. The costs just seem too high to make it even remotely worth while. My character currently has a +4 Holy bow, which doesn't incur a -3 penalty to attack rolls that reduces its effectiveness to a net +1.
