Mordenkainen's Lost Notebook
6-level Transmutation
This spell functions like the Mordenkainen’s faithful hound spell, except that the phantom hound can also track a creature you designate using the Survival skill. Its Survival bonus for this task is equal to your spellcasting ability modifier + your proficiency bonus. A trusted bloodhound has a movement speed equal to yours and can move at full speed without taking a penalty on Survival checks to track. While tracking, a trusted bloodhound can’t attack or have any other effect on combat. However, as an action, you can instruct a trusted bloodhound to function identically to Mordenkainen’s faithful hound. As an action, you can command a trusted bloodhound to resume tracking.