Broodmother

"First day, they come and catch everyone... Second day, they beat us and eat some for meat...  Sixth day, her screams we hear in our dreams...  Ninth day, she grins and devours her kin...  Now she does feast, as she's become the beast..." In the subterranean halls of the dwarves, a nightmarish creature called a Broodmother

is spoken of in hushed and terrified whispers. The few who were lucky to return from battling the plaguing dwarven lands seemed mentally broken by the experience, feverishly mentioning tales about a disturbing beast known only as a Broodmother. What the Broodmother is, and what it is doing underground is a complete mystery. However, one thing does stand out across all these stories –- its insatiable hunger for Grey Warden flesh. Branka allows this creature to live, so she might use its children as test subjects for the traps that await those who seek the Anvil of the Void.

Lore
It is well-known that darkspawn carry off those captured in their raids to underground lairs. Most assume that the prisoners are eaten, or somehow tainted and turned into darkspawn themselves, though this could never account for the sheer numbers of the horde. Forays made by Grey Wardens into the underground have uncovered the answer. When exposed to the darkspawn taint, men are driven mad and eventually die. Women, however, undergo great pain and gross mutations that cause most of them to perish. Those that survive, however, become the grotesque broodmothers. These giant, twisted behemoths birth many darkspawn at a time; a single broodmother can create thousands of darkspawn over the course of her lifetime. Each type of darkspawn is born from a different broodmother: Humans produce hurlocks, dwarves produce genlocks, elves give birth to shrieks, and from qunari are born the ogres.

Strategy
The broodmother guarding the Anvil of the Void is a dangerous opponent, despite her immobility. She has the following known attacks and abilities:
 * Spit: The broodmother expectorates a vile toxin, which splashes a moderate area around its target for high nature damage. Spit requires line of sight.
 * Broodmother Tentacles: The broodmother has four Elite tentacles, which protrude from the ground. Each tentacle can make melee attacks for moderate damage. The tentacles can retreat back into the ground and emerge anywhere that is coated in the broodmother's ooze. The tentacles have high health, and maneuver themselves to avoid Area of Effect attacks by surrounding a character so that AoE damage abilities must hit that character as well as the tentacles.
 * Summon Darkspawn: The broodmother is able to summon a raiding party of darkspawn at least once during the encounter. This group consists of several genlock rogues and archers.
 * Crush: The broodmother will lift a character into the air if that character is standing directly in front of her. She will crush them and most likely kill them with this attack.

The battle area has three critical terrain features. First, all exits from the room are blocked by additional tentacles, making retreat impossible. Second, the broodmother's ooze covers the floor. The tentacles can only emerge from ooze-covered areas. Third, on either side of the broodmother are two stone paths which lead up and behind her. She cannot be attacked directly from these paths, but she also cannot attack anyone standing there, and her tentacles cannot emerge from there.

One easy strategy for this fight involves the use of large-area damage spells such as Tempest, Blizzard, or (in a pinch) Fireball. Stand on one of the stone paths and cast these spells down. The darkspawn will have to come up the path to attack the party, who will be beyond the reach of the broodmother's spit and tentacles. Though time-consuming, this is a safe and easy way to win a very difficult battle.

Another strategy is to keep your player controlled character to the right or left of the broodmother's body. This will ensure that she cannot lift the character into the air but will give direct access to the broodmother herself rather than a focus on one of the tentacles. You should also make sure that all of your active party members have one of their tactics changed to allow them to heal themselves should their health drop below 50%. Make sure you have a lot of health poultices available for this battle.

The broodmother has a special execution animation if killed by a melee attack.

Source
IGN