Marmaduke

Before pursuing Marmaduke, you must complete the Siren Isle intro campaign quest chain up to The Radiant Vault. Paste this into chat to check if you've already done it: /run print(C_QuestLog.IsQuestFlaggedCompleted(84724))

Head to the entrance of The Forgotten Vault at 44, 24 on Siren Isle and run down the corridor to the last room. If you have the Seafury Tempest debuff, right-click it to remove it before entering, as the storm phase will prevent you from seeing the journal.

In the final room of The Forgotten Vault, find the skeleton near the large crystal. On the ground nearby is a journal that offers the quest The Tattered Journal — pick it up to begin the chain.

Follow the quest chain through Scattered To The Winds, A Group Effort, and Laid To Rest At Last. You can verify completion by pasting this into chat: /run print(C_QuestLog.IsQuestFlaggedCompleted(85573))

Once Laid To Rest At Last is complete, return to the upstairs of the Inn and find the Well Loved Squeaky Toy on the floor next to the far bed.

Head out to find Marmaduke, who patrols between the bottom of the Inn's cliff and the town at around 58, 48. If you can't spot him, use the macro /targetexact Marmaduke since he walks around. Give him the Well Loved Squeaky Toy to complete the chain and collect him as a pet.

With Marmaduke summoned, visit his pillow inside the Salt and Shanty inn at 39.34, 54.26. Once you no longer have the Well Loved Squeaky Toy in your bags, click the item on the pet near his pillow to loot 5x Marmaduke's "Ducky Friend", which you can use while targeting Marmaduke. There are also graves behind the Salt and Shanty at 38.78, 54.72 that Marmaduke will react to when you walk near them with him summoned.