I haven't played Dragon Knight before and I was wondering if he can use something similar to the Knight's Bravery potion or the Elven Wafer?

Yes I believe it's the level 30 quest spell. Blood boil or something? Takes an ingredient but it does act as a brave.

**Edit: Found it it's Bloodlust
https://l1justice.com/lineage/database/skills/186/

Cool, thanks Mathky :)

Is the ingredient Bone Fragment? Do you know which mobs drop it?

 

 

Its Forbidden Fruit for brave, you can buy them in warp 10, north of where you come in at. 

Bone Frags are for the Awakening skills.

Oh okay, so Forbidden Fruit acts like braves, thanks Soundwave666

And where do you get these Bone Frags?

I found the Bone Fragments, they were sold at the same merchant in Behimos.

The weird thing is, I can't use the Forbidden Fruit, it says "Your class can't use this item." when I try to use it...

Is this a level thing? Or do I need a certain skill before I can use them?

It seems like you need both fruit, and skel frag to use bloodlust. It consumes both. Not sure if this is intended or not. 

Strange... on this page it says you only need item 49157 (Bone Fragment). Could it be a bug, or hasn't the page been updated?

I believe this to be a bug. I think the intended usage is:

Both Illusionist and Dragon Knight use Forbidden Fruit as brave.

Dragon Knight uses Bone Fragment for casting certain spells.

Illusionist uses Blessed Elemental Stone (or whatever) for casting certain spells.

The Skill Bloodlust should consume Forbidden Fruit to cast (Think of it like a magic gem for mages?)

Awakening (Faffurion, Anthras, Valakas) Should consume Bone Frag.

Not sure why this is diffrent here, maybe just switched on accident? I'll link this post to the GM's and maybe one of them can comment.

Can someone post a link to a Korean (or JP, whatever works) source on this?

Bloodlust

http://power.ncsoft.jp/lineage/powerWiki/%E3%83%96%E3%83%A9%E3%83%83%E3%83%89%E3%83%A9%E3%82%B9%E3%83%88

If you translate to english it says 

 

Performance changed with Advance Update II. Pull out the potential dragon's power and improve the speed of action for 300 seconds. Consume one yggdra fruit at the time of use.

 

For the Awakening skills it says "Cunsumption item: 1"  but it does not specify what item that is, that i can find.

 

 

Sounds like you were right.