Ost is an untakeable freep keep which holds the relics needed to give creeps an infamy boost in the Ettenmoors.  The creeps must enter the keep, kill the CG, then run the relic back to DG without dying or being feared.  A failed attempt results in a 30 minute reset timer.  Additionally killing the CG and FM's is worth 2k Destiny and a title.  It is extremely hard if there are freeps, but doable if taken slowly.

The difficulty of Ost varies with how many of the three central keeps (TA, Lug, and TR) are blue.  This influences the respawn rate and the appearance of FM's along with the CG.  Overall though, the following points are useful in going through Ost.

1. Everyone must stay up with the Raid leader, no one should be firing at range
2. No one releases if killed, they won't make it back through the respawns

3. No one shoots at freeps unless they're told to.  Ranged only on freeps at that point.

Assault

1. Gather everyone up together at the bottom of the Ost ramp
2. Clear the entryway from the outside, pull the FM (it's a fake one) out and kill him
3. Enter and move to the campfire on the right, clear all aggro'd NPCs.  Ranged takes out Coldfell Hunters.
4. Go NE diagonally to the other campfire and clear the NPCs
5. Move to the bottom of the stairs and kill the FM and NPCs
6. Move to the top of the stairs hugging left, kill the three NPCs
7. Clear the rest of that ledge, this is a reasonable rest spot
8. Pull the LT that patrols the hallway and kill him
9. Go straight through the next doorway and go far right.  Kill the adds then the FM.  It is important to stay away from the doorway because the hallway LT will respawn and aggro onto anyone near the doorway.  This is a rest spot
10. Pull the hallway LT and kill it again
11. Hug the left wall and go up the stairs, kill the LT without aggroing the FM
12. Cross to the other side of the room and fight the FM in his corner watching for the patrolling LT
13. Kill the patrolling LT
14. Enter the CG room hugging left and go into the far wall.  This is a rest spot
15. Set up two tankers, one for a FM (if present) and the other for the CG.  Everyone else will be on the last FM.  The raid will pull their FM then the tankers will grab their targets and drag them back to where their spawn point was.  The rest of the raid must stay tight in the corner else the LT in the hallway will respawn and aggro anyone in the doorway area.  As one target goes down, a tank pulls his target to the raid for destruction.
16. To exit, go to the previous FM's room and jump out the window (don't jump too far else you'll end up in the camp)