真‧三國無雙４ Special (pc game) Help! (15)

I want to ask you some 關於真‧三國無雙４ special :
1.I want to know 左慈 冥天照符 (weapon) is black. Is it ouly have one black colour weapon?
2.I konw 左慈 冥天照符 《版圖》虎牢關之戰 - 連合軍
《條件》擊倒呂布後貴重品發現
《位置》洛陽城右下方城牆
But what is the weapon 貴重品's colour,is it a box in it? Is it have any picture can help me to find 冥天照符?
3. 呂布是不是很難打, 怎樣才能K.O 呂布?
4. In 虎牢關之戰 - 連合軍 ,do I need to 設定難易度是困難或以上 to take 冥天照符?

Thank you!