EQ2 Zam says Lord Ree drops them, but I downed him about 10 times today and didn't get one. Who/what drops them?
They are a rare drop from an exquisite chest from any level appropriate heroic mob. They can also be a quest reward from tradeskill apprentices after you do some work for them. If you have the plat, you can pick one up on Maj'Dul for 5,445.
I've been camping Lord Ree for a couple days straight. I've gotten every 10-15 master spell for the Illy and Necro I'm using to camp him (so a LOT of exquisite chests), and not ONE reactant. There's got to be something wrong with the loot table, they just aren't dropping. Unfortunately, I'm on Skyfire, and the cheapest one is 20k, with a bunch at 100k, and I'm not paying that much for a tier 2 item.
Another way is to make an alt and get crafting up to that tier and do the crafting apprentice item every day. I have only gotten reactants from apprentices unfortunately. They will only give the ones for the level of crafter
The key part of my post is that they are RARE. They also have the possibility of dropping from exquisite chests from other heroic mobs, not just Lord Ree. Try some of the others in The Commonlands/Fallen Gate. I found I got the most reactants, as Soara2 says, through the tradeskill apprentices. By the time you level one of those though, you will likely have out-levelled the need for armour or weapons made with this level of reactant.
What is your toons name on SF? I will check when I get home from work whether I have one or more. Rhodris is right, Lord Ree is one of many sources that can drop it. Camping one mob for an ultra rare drop is going to be an exercise in futility. We're talking significantly less than 1% here on the drop rate. Maybe not Ethereal Drop rare, but definitely it's not efficient to try to farm for it rare.
Just running around the source zones where it drops and ignoring what you are specifically hunting for will probably result in getting it faster. Just go out and zip around, do the content have fun. Get whatever drops, you will probably get one and enjoy things a lot more than just grinding, grinding, grinding, until your eyes bleed.
Most of the ones I have looted have been from the Graveyard or the Sprawl. It's rare to see one. A while back they changed the level of the gear crafted from 10 to 12 effectively stripping a lev 10 toon I have had locked and decked out in Humming gear for years. I had a few choice words for the person who made that decision
I do have one if you still need it. My characters name on SF is Melkior (I'm creative with names you see) if you want to send me mail or a tell.