If you’re killing these for the shard I suggest you go to the site to get the map
http://maps.eq-toolbox.com/files/TheDeep_1.txt
Save the file in your EQ / Maps folder. Note: The one from eqatlas only has a single line for the bridge as of my download and you can easily fall (ouch), eq-toolbox has both sides of the bridge showing.
You need to cross the invisible bridge. There is a translucent bridge there that is false. You can't levitate in the zone and if you fall you take 20K.
You can invis all the way to these, but careful as some mobs see invis on the way (only ones I found that see invis are the ones that wander, often you can wait for them to move away). Once across the bridge turn left and pass the 'An Ancient Shrieker' area and you will see some 'A Horror Guard', 'A Thought Horror Evocer', and/or 'A Thought Horror Spiriter'. You should be able to single pull the first 5 at least, there are 2 more deeper in that I didn't try as the spawn rate is pretty fast.
'A Horror Guard' has about 12K hps, doesn't cast spells - didn't resist any of my spells after a debuff took.
'A Thought Horror Evocer' has 8-10K hps, is a Enchanter mob, casts spells, but easy to resist with resist magic on. Dispells and debuffs you so make sure you have junk buffs on to reduce the chance of losing hp or mana regen buffs. Will try to charm (Facination?) you.
'A Thought Horror Spiriter' has 8-10K hps, is a Necromancer mob, casts spells, but easy to resist with resist magic on. Dispels and debuffs you so make sure you have junk buffs on to reduce the chance of losing hp or mana regen buffs. Will try to fear you.
All 3 mobs are rootable, slowable and don't summon. I talked with someone who got a shard after 15 or so kills, took me about 18 in all from these 3 mobs combined.
One last thing there are thought leech’s, those don’t drop the shard, the horror’s are the ones that do. Hope this info helps.