The poems refer to 3 poems in the game written by Douglas' brother Victor. His poems can be found in various bookshelves throughout the game, he is known as "Victor Gavelinus".
One is in the Bavelock Library in the first bookshelf (to the right) on the second floor.
One is in the bookshelf next to Arl in Bavelock.
One is in the bookshelf next to Bethana in Savina.
Finding all of them will unlock the 'Soul of a Poet' medal and will give you the 'Masquerade mask'.