[blutorange]

上に下がる makes no sense. に marks the target. This would mean "To descend to heaven", ie "to go down to what is above".
"From above" is 上から・上より. Although 天国・天・天界・空 &c. might me more appropriate according to context. And as for "descend", 降り立つ sounds much better. And you may want to consider "我", depending on how you want it to sound.
(eg 我は天界よりこの世に降り立ちた神様の贈り者なのだ！ )　(with the pun between 贈り物 and 送られた者 intended...)