I think the best way to understand a character is by hearing what they have to say. Valgarv is a great example of this, having said quite a few memorable and philosophical quotes throughout Slayers TRY. I've archived some of the ones that really stood out and you can read them below, in chronological order.

EPISODE 3: Where is the impudent person going?

Valgarv (to Lina): I see. The great and powerful sorceress is just an arrogant fool.

Lina: Who the hell are you?
Valgarv: Me? Let me show you. Take this with my fondest regards! (proceeds to attack)

Valgarv: Brings back memories... I needn't worry about losing to you weaklings.

EPISODE 4: On the go! The guy is aming to kill!

Valgarv (to Lina): Now the real fun begins.

Valgarv: Time to go to hell!

Valgarv: Now give me the damn sword!
Gourry: You'll have to kill me first!
Valgarv: How cute. Don't try too hard.

Valgarv: Five versus one? That's not very fair, now is it?

Valgarv: God damnit! Remember this, Lina Inverse... I will be back to kill you!

EPISODE 8: Careful preparation! The plan starts moving!

Valgarv: Is this what god's people are forgiven to do?! [Commenting on how the Golden Ryuzoku slaughtered his kind.]

Valgarv: I'm going to take care of Lina Inverse, as revenge for Gaav-sama!

Valgarv: Ryuzoku... Mazoku... Humans. If all of them are going to come in my way, then I'll crush them all!

Valgarv: Golden ryuzoku, are you saying that it was our fault that we were killed? That's not true!! You golden ryuzoku feared us, our powers, feared that you might be kicked off as the most powerful of the ryuzoku!

EPISODE 12: Delirious! In persuit of the mystery!

Valgarv: Just wait. I'll end everything soon... everything!

EPISODE 13: Instant explosion! The person who holds the key!

Valgarv: Shut up! Shut up! Shut up! You mazoku are no different! The mazoku feared Gaav's power and judged him unfairly.
Xelloss: Well, yeah...
Valgarv: I don't need to hear the reasons of why my people were destroyed from a mazoku! Gaav was the only one who saved me and I will not forgive you mazoku who opposed him!
Xelloss: Then your answer is "no?" [Referring to his question of whether or not Valgarv wanted to join the mazoku.]
Valgarv: THIS is my fucking answer! [Throws a powerful attack at Xelloss.]

Xelloss: If you were to reject our proposal, then I would have to kill you. Now you are my enemy.
Valgarv: You were my enemy from the start.

Xelloss: Let's end this soon.
Valgarv: That's my line!

Gourry: How dare you hurt Xelloss... [Pulls out the "Hikari no Mallet. "]
Valgarv: ............ ._.;

Valgarv: This place is the door to the ruins. And also your graves!