The Last Straw is received after the completion of Best Served Cold, the version differs if either Orsino or Meredith was supported during Showdown, the opening quest of Act 3.
Letter 
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If Hawke supported Meredith...
Champion,
You have proven yourself a friend of order in this city, and I find myself in need of your support once again. Dire events are underway at the Gallows which could tear the city apart. I believe the Champion's appearance could make all the difference, and thus I ask you to come as soon as possible.
Knight-Commander Meredith
If Hawke supported Orsino...
Champion,
You have proven yourself a friend to Kirkwall's mages and it seems I must call upon you once again. Meredith has gone too far, and I will not let her madness remain unchecked. I ask that you come to the Gallows at once. Perhaps together we can stop this before there is bloodshed.
First Enchanter Orsino
