What is a true 'Guru'? (from the Kula-Arnava-Tantra)

"There are many gurus, like lamps in house after house,

but hard to find, O Devi,

is the guru who lights up all like the sun.

There are many gurus who are proficient in the Vedas and the Shastras,

but hard to find, O Devi,

is the guru who has attained to the supreme Truth.

There are many gurus on Earth who give what is other than the Self,

but hard to find in all the worlds, O Devi,

is the guru who reveals the Self.

Many are the gurus who rob the disciple of his wealth,

but rare is the guru who removes the afflictions of the disciple.

He is a [true] guru by whose very contact there flows the supreme Bliss.

The intelligent person should choose such a one as his guru and none other."

(Translation from Feuerstein's 'The Yoga Tradition')