How writing poetry was compared to Perseus killing the Medusa Gorgon

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When thy song is shield and mirror

To the fair snake-curlèd Pain,

Where thou dar’st affront her terror

That on her thou may’st attain Perséan conquest

Francis Thompson wrote those lines.. see below
I am interested in these lines from the poem below…. When thy song is shield and mirror To the fair snake-curlèd Pain, Where thou dar’st affront her terror That on her thou may’st attain Perséan conquest; I think the meaning is that by expressing what is in us creatively in poetry or other forms we can overcome what we are afraid of not by attacking and killing it but indirectly in the manner of Perseus who killed the Medusa Gorgon by locating her and seeing her reflected in the mirror of his shield.Others had been turned to stone by her gaze.
Expression is the mirror/shield
Read about Perseus below http://www.greekmythology.com/Myths/Heroes/Perseus/perseus.html 
This is where I got the poem………Bartleby.com a good website re which I say go visit. Nicholson & Lee, eds. The Oxford Book of English Mystical Verse. 1917. 240.
From ‘The Mistress of Vision’ By Francis Thompson (1859–1907)
WHERE is the land of Luthany, Where is the tract of Elenore? I am bound therefor. ‘Pierce thy heart to find the key; With thee take 5 Only what none else would keep; Learn to dream when thou dost wake, Learn to wake when thou dost sleep. Learn to water joy with tears, Learn from fears to vanquish fears; 10 To hope, for thou dar’st not despair, Exult, for that thou dar’st not grieve; Plough thou the rock until it bear; Know, for thou else couldst not believe; Lose, that the lost thou may’st receive; 15 Die, for none other way canst live. When earth and heaven lay down their veil, And that apocalypse turns thee pale; When thy seeing blindeth thee To what thy fellow-mortals see; 20 When their sight to thee is sightless; Their living, death; their light, most lightless; Search no more— Pass the gates of Luthany, tread the region Elenore.’ Where is the land of Luthany, 25 And where the region Elenore? I do faint therefor. ‘When to the new eyes of thee All things by immortal power, Near or far, 30 Hiddenly To each other linkèd are, That thou canst not stir a flower Without troubling of a star; When thy song is shield and mirror 35 To the fair snake-curlèd Pain, Where thou dar’st affront her terror That on her thou may’st attain Perséan conquest; seek no more, O seek no more! 40 Pass the gates of Luthany, tread the region Elenore.