Grand Cleric Iona is a war table mission in Dragon Age: Inquisition.
Acquisition
Complete The Chantry Remains with Leliana or Cullen and and complete the quest "In Hushed Whispers" or "Champions of the Just". May also require a certain Inquisition level.
Operation Text
While the Chantry is ostensibly the Inquisition's ally, a cleric has risen as the leader of those who oppose it. Grand Cleric Iona of Cumberland has quietly gathered them around her, giving her an early lead in the race to become the next Divine. Should she succeed, this could mean a resumption of widespread opposition to the Inquisition... as well as danger to the Herald of Andraste.
Advisor Suggestions
She has rivals. We should pick one, and give that cleric whatever ammunition we can muster against Grand Cleric Iona.
Leliana -
Grand Cleric Iona has no secrets, but she is dangerous—she has hooked her wagon to this issue alone. We cannot let it take her to the Sunburst Thrown. She must be silenced.
Cullen -
A display of force and a warning are all we need. She is not a fool, and will realize the Templar Order no longer protects her.
Results
I had a productive meeting with Revered Mother Anastasia, who is not seeking the Sunburst Throne itself, but does not want Grand Cleric Iona to achieve it. They are both from Nevarra, so I suspect there is bad blood. Either way, a few favors spent and Anastasia had the power to shout Iona down quite convincingly. The matter is considered dropped, and the revered mother sent us gifts as an expression of her appreciation. Josephine
Grand Cleric Iona has disappeared, thanks to an operative by the name of Argent. While the act cannot be traced back to us, the rest of the Chantry is clearly under the assumption that her tirade against the Inquisition is what led to her fate. Unfortunate as this was, we have gained support among the remaining clerics... none of whom wish to be on our bad side. Leliana
There was some initial ranting on the part of the grand cleric, but I think the constant presence of Inquisition soldiers outside the doors of the Grand Cathedral serve as enough of a reminder to quiet the other clerics. Some grumbling remains, but the danger appears to have passed; they've moved onto other concerns. Cullen
Rewards
Josephine: 30 Influence, Cassandra 
Approves
Leliana: 30 Influence, Cassandra Approves
Cullen: Amulet of Power (Cassandra), Cassandra Approves