Here are the lyrics to 'One Winged Angel' AKA Sephis theme. Y'know, that awesome one that noone knows any words to except 'SEPHIROTH!' lol.

[CHORUS]
Estuans interius
ira vehementi
Estuans interius
ira vehementi
Sephiroth
Sephiroth
[REPEAT CHORUS]
Sors immanis
Et inanis
Sors immanis
Et inanis
[REPEAT CHORUS]
Veni, veni, venias,
Ne me mori facias
Veni, veni, venias,
Ne me mori facias
[REPEAT VERSE]
Veni, veni, venias, (Gloriosa)
Ne me mori facias (Generosa)
Veni, veni, venias, (Gloriosa)
Ne me mori facias (Generosa)
[REPEAT VERSE]
Sephiroth
Sephiroth

Well, no idea what the fuck language that was, latin probably, but here's the english translation:
[CHORUS]
Burning inside
with violent anger,
Burning inside
with violent anger,
Sephiroth
Sephiroth
[REPEAT CHORUS]
Fate - monstrous
and empty,
Fate - monstrous
and empty,
[REPEAT CHORUS]
Come, come, O come,
do not let me die
Come, come, O come,
do not let me die
[REPEAT VERSE]
Come, come, O come, (Glorious)
do not let me die (Noble)
Come, come, O come, (Glorious)
do not let me die (Noble)
[REPEAT VERSE]
Sephiroth
Sephiroth