Kill Bloodhound Knight while summoning Blaidd
This square requires you to defeat Bloodhound Knight Darriwhil, the boss in the Forlorn Hound Evergaol in Limgrave, while summoning Blaidd the Half-Wolf. In order to be able to summon Blaidd, you need to talk to him after using the Finger Snap gesture in the Mistwood Ruins, which makes him drop to ground level.
To obtain the Finger Snap gesture, you can either talk to Kale after you heard the wolf noise next to Mistwood Ruins, or kill Kale (the fastest option as it does not require traveling to the location first). Blaidd's summon sign will be available inside the evergaol after talking to him.
Blaidd does not need to survive the fight for the square to count. He only needs to be summoned. This square has synergy with Complete 4 Evergaols.
Darriwhil counts as a Limgrave/Weeping Peninsula boss.