In Chapter 7 in Valor Mortis, you get introduced to the Mice – children who believe in the Shrike so much so to have made up an anthem in her name. When you first come across a burrow (and you will find several such all over The Outskirts area); you will get this poem, but with missing stanzas.
There are a total of 4 to find, and in this guide, I have put up the locations for all these, along with the rewards for completing The Shrike’s Anthem in Chapter 7: Witch Hunt, in Valor Mortis
Starting The Shrike’s Anthem side quest

You can begin the side quest by interacting with any of the burrows where you find the stanzas for completing the poem. However, to proceed in the intended manner, pick up a note on the main path from the Island of Whispers Lantern. Note the symbol on the wall, anytime you see a similar symbol – means that the next progression for The Shrike’s Anthem is somewhere nearby.
Shrike’s Anthem – Second Stanza

When progressing from this area, you will notice a bridge that you can cross. Before you do that, look left, and you will see a drawing done with chalks. Take out the Howlers that mob you, and enter the building and climb up to locate the burrow, which gives you the 2nd stanza for the poem.
Shrike’s Anthem – Third Stanza

The next stanza is also nearby. Cross the bridge, clear the area of enemies, and if you look to the left, you will see the familiar Shrike symbol. Enter that building, and you will see a crawl space. Enter that, to find the burrow, and the next stanza for The Shrike’s Anthem. We are almost done with this, and have 1 more stanza / note to hunt for.
Shrike’s Anthem – Fourth Stanza

Now, continue along the main path, and once you come into an open area, stick to the right, hugging the river. You will see a set of submerged buildings, where you can jump across rooftops, as I have shown above. From the first building, look left, there will be another ledge that you can use to get into the building. The next stanza is found there, interact with the burrow to progress the quest. One, and final stanza now left.
Shrike’s Anthem – Fifth & Final Stanza

Now, progress along the main quest, till you come across the gate as I have shown in the image above, with the 2 posters of Napoleon. Go through that gate, and take a left. You will enter into a house with narrow passageways filled with enemies. At the end of it, there is a ledge that you can climb on to, and there are multiple pathways leading out of it.

If you look up, you will see the familiar Shrike symbol, and there will be narrow boards that can lead you to it. Get there, interact, and you will receive the final missing stanza.
You get a Tiny Whisker’s Gift on completing this quest. For once, unlike Sleeping Beauty, The Curious Case of Seamus Diggory, or In the Name of Art side quests, there are no Ambers, or trophy unlocks for this one. Though you did get to read how the Mice worship the Shrike and the poem that they have written as an ode, so that’s something.
