It is true that Lucifer in a biblical point of view is connected to Satan and appears in the myths as one and the same character.
However, Lucifer, the light-bearer - the one that brings the light- referred in the bible originally to a 'morning star' which was used as an allegory of the king of the Babylon. That in the book of Isiah is - as far as I have understood - is the only mention of 'Lucifer' in the bible.
Lucifer and the Devil were melted into a one character around the 1st century BC.
The name 'light bearer' was not seen to fit the character of the Devil, so they (St. Jerome) changed it to 'Satan' that derives from Hebrew origin meaning 'the enemy'. However Lucifer as a 'morning star' stayed in the bible.
Blavatsky was the primus motor for theosophy. The cosmology of theosophy I myself find quite complex as well as their demonology.
As far as I have understood, Christ is seen as the ultimate good in the cosmos. On the other side we have Lucifer, the spirit of the heavens and - and this is the interesting bit - another devlish being, this time of the earth - Satan ('Ahriman', which is sometimes used. This name has a Persian origin.)
Now the purpose of life according to theosophy is to develop spiritually. In this one needs help from the spirit of the heavens, Lucifer.
Lucifer becomes devil-like if one consertrates too much on one's own personal spiritual development and forgets the good deeds inspired by Christ.
Also in the quote from Blavastky, it is said that Lucifer should save us from animalism, from the Satan (Ahriman), the evil spirit of the earth.
It all sounds like a $2 fantasy book, doesn't it?
I hope this clears a bit what I ment in my previous post, Stranger. Even in the biblical sense all different devils are one and the same entity, historically they might have different origin.
So if a theosophist prays Lucifer to help her to gain knowledge from the higher worlds, it is for her spiritual development. And the more spiritually developed you are, the more Christ-like you are.
That's why I say theosophic cosmology is complex.
Please note, the above does not necessarily reflect my personal believes.