TOWER OF ISHAL
Walkthrough
The Tower of Ishal is a main quest that takes place during the Battle of Ostagar. King Cailan personally requests the Warden and Alistair to light a beacon atop the tower, signaling Loghain's forces to support the king's and Grey Wardens'.
Start off by travelling towards a nearby bridge (Ostagar Map, L7) and once you're close enough you'll be rewarded with an interesting cut-scene. Head forward, ignoring all the fights and explosions taking place in your vicinity. You should be heading towards Ostagar - Tower of Ishal. Once you've arrived at your destination one or two NPC's will join the team (a mage will join if you're a warrior/rogue class and soldier will join if you had the magi origin). Make sure to equip your new allies, because you'll need them to finish this quest. Enter the tower grounds (this is the area that was inaccessible up till now).
Keep heading north-east and don't be surprised by the fact that a lot of hurlocks and genlocks will stand in your way. Try using the mage in your team to cast powerful spells and don't forget to keep your archers and mages away from the main battles. Remain in one area until you've defeated each group and don't forget to spot and kill enemy archers sooner rather than later. Eventually you'll make your way to the main gate of the tower (Ostagar M1, 9) and this is where you'll meet an alpha Hurlock. Use the same tactics as before and you should be fine.
Opening the main door will result in your team travelling to Tower of Ishal - Ground floor (Tower of Ishal Map, 1).
Tower of Ishal First Floor
Make your way into the center of the floor. There will be a tripwire that sets off a grease trap that a nearby Genlock emissary will try to set alight with a Fireball
Whether you actually set off the trap or not, the emissary is scripted to cast just that one Fireball during the encounter.
If you cannot disarm the trap, you may be able to squeeze past without triggering it by hugging the pillar to the right.
Alternatively, command the party to Hold and leave them out of line of sight; then move one character out to get the attention of the Darkspawn (e.g. with a crossbow, for long range), and then move everyone behind cover. This should give at least one hurlock at a time no choice but pursuit. Only the emissary may double back after falling for this trick. Also note that the grease will eventually dissipate, whether or not it is set aflame.
If you have it, activate Indomitable and you'll be able to walk right through the grease, fireball and ensuing fire without being knocked over.
The emissary is supported by several pairs of bow-wielding hurlocks spread across the space. Take the emissary down first since it can Heal (and regenerate Mana), then finish off the hurlocks. The next rooms contain genlocks (to the right) and hurlocks (to the left). The foes on one side will usually (but not always, or not all together) come to the aid of the other side when combat starts.
Note: You can loot a Silver Bracelet from a Wooden Chest by one of the bunks.
The final room contains more genlocks and a stairway to the second floor.
Tower of Ishal Second Floor
There are significantly more genlocks and hurlocks on this floor, and they will charge as the party makes its way into the large semi-circular room on this level. Fortunately there are also some ballistae nearby, which can be used to impale melee fighters and knock down genlock archers (try to avoid Friendly Fire incidents).
Another tactic is to clear out one of the narrow rooms next to the main force of Darkspawn. Then, from inside that room, use some powerful indirect spells on the Darkspawn (such as Paralysis Explosion) before attacking them.
Look out for a Discarded Book which unlocks the Codex entry: The History of the Chantry: Chapter 1. The book is on the floor in front of a bookshelf on the tower's east side.
Note: If you triggered the enemies without opening the doors on either side as you walked through to the outside part of the floor, the enemies will open the doors themselves. Make sure to go into both rooms for containers of loot after finishing the enemies off.
Tower of Ishal Third Floor
Fight past the genlocks in the first room. In the second room are more genlocks supported by a Genlock alpha. Alistair will suggest using the lever to release the dogs (mabari hounds) caged in this room—the dogs will help you take down the genlocks and other enemies on this floor. You can loot a Warden Recruit Shield from the alpha, as well as Warpaint of the Wolfhound from a locked Wooden Chest.
Between the Mabari cages and the stairs to the Upper Floor are three more rooms of darkspawn and crates (the latter are consistently heavy on Lesser Injury Kits). It is advisable to lure the enemies out so the friendly dogs can join the fight. The final room contains a hurlock, two genlocks, and the stairs to the upper floor.
Make sure to SAVE YOUR GAME before heading up to the top.
Tower of Ishal Top Floor
A short cutscene reveals an ogre enjoying a grisly feast. Kill the ogre
I would recommend that at least two members of your team should begin attacking the beast from the distance, because ogre's direct attacks can take a lot of damage. Besides your mage or your rogue can stun/paralyze the opponent and it'll make the process of injuring the beast a lot easier.
Keep attacking the ogre with a team divided to mages/archers and warriors. Don't forget to take special care of less resistant members of your squad, because they can die almost instantly if the ogre gets to them. It's also important to keep using all the abilities you've unlocked so far to increase chances of scoring good hits or to make ogre's attacks less powerful.
Then you unlock Codex entry: Ogre. Afterwards, loot Havard's Aegis (which comes with Codex entry: Havard's Aegis) and a Journeyman Lightning Rune from the ogre's body. Don't miss the two Barrels containing a Tribal Necklace and random other loot. Once finished, light the beacon.
Note: Anything worn by your companions except Alistair (and Dog if you're a Human Noble) will be lost after you light the beacon. Consequently, if you wish to keep their equipment or any other extra items you equipped them with, unequip them, before you proceed.
After the Battle of Ostgar & Tower of Ishal
After watching the awful conclusion to the Battle for Ostagar (which unlocks Codex entry: Ser Cauthrien who you see in the cutscene and is Teyrn Loghain's right-hand)
Then you and Alistair will be overcome (nearly instantly, in a cutscene) by yet more darkspawn.
You awake (undressed, in a bed, in a hut) to see Morrigan, who can inform you that Loghain quit the field; that the king and the Grey Wardens were slaughtered; and that her mother rescued Ferelden's only two living Grey Wardens (by transforming into a giant bird and plucking them from the Tower) and has been healing them at her home. (The human noble's Dog, if applicable, isn't mentioned, but survived as well.) If the Warden is persistent in the pursuit of details, Morrigan will relate that the darkspawn are feasting on the dead... and dragging survivors underground.
After questioning Morrigan, recovering inventory and stepping outside, the Warden finds Alistair and Morrigan's mother, who now introduces herself as Flemeth (unlocking Codex entry: Flemeth). The next course of action is discussed; the Wardens decide to use their Ancient Treaties, and Alistair suggests approaching Arl Eamon of Redcliffe as a potential ally against both the Blight and Teyrn Loghain (also unlocking Codex entry: Arl Eamon Guerrin).
Flemeth also insists that Morrigan accompany the Wardens - suggesting that they consider it "repayment for your lives" if that will make it easier to accept. A generous welcoming of the newest companion can earn up to (+8) from her, and if prompted she advises proceeding to the village of Lothering to gather news and supplies. Alistair should give (+4) if his input and hesitations aren't treated too rudely; he is still somewhat overwhelmed by the massacre of his entire order in Ferelden (especially the loss of Duncan), and his personality clash with Morrigan has only just begun, but he ultimately accepts that any help is vital and should be accepted.
Before the group's departure, Flemeth may be approached for a few more morsels of wisdom and background information; Alistair may be asked many of the same questions soon to be available in Camp, and have his approval modified accordingly.
Once the conversation ends, the quest Lothering and the Imperial Highway commences.