The Attack Dog spell causes the target to behave like an attack dog.
Rowena later used the spell on three angry college students in an attempt to kill Dean, but the attack failed. She then leveraged their lives to force Dean to let her go.
Rowena cast the spell on the angel Castiel, making him attack Crowley. After apparently killing Crowley, Castiel regained control of himself but remained under the effects of the spell which would cause him to go into powerful rages and attack people at times. It also allowed Castiel to telekinetically push spikes out of his head while in a rage despite his powers being blocked by a set of Supernatural Handcuffs. Another time, he was able to break free of the handcuffs completely. The angel Hannah was unable to break the spell which had "dug in deep" or heal him of his injuries from torture. Castiel later told the Winchesters he felt like "tomato salsa in a blender on puree" as the spell did its work in which he was the tomato, indicating that the spell was ripping him apart. Rowena indicated the spell was just taking longer to have its usual effect on Castiel because she told Dean if she didn't reverse the spell, Castiel would "go foaming at the mouth and die." The Winchesters were eventually able to find Rowena and force her to reverse the spell before it could take hold of Castiel completely.
The spell required a hex bag to be held by the target and an incantation to activate the spell. The incantation is as follows:
- Impetus bestiarum. (means "attacks of beasts")
As soon as the incantation is over, the target would appear to be overcome by pain. They would lose human consciousness and act, behave, and even sound like an attack dog. The spell causes the target's nose, and later, the eyes to bleed and for them to ultimately die. Rowena stated that the person is consumed by the spell but she is able to prevent this aspect of it if she so chooses.
In Brother's Keeper, Rowena was capable of using this spell without the hex bag. She was also able to affect Castiel, even though he is a Seraph, and forced him to attack Crowley. Additionally by using certain Latin incantations, it will amplify the rage and physical powers of any affected target to a certain degree, leaving even Crowley's fate to become uncertain. The following incantation is:
- Dele malum hoc (means, Destroy this evil (being))
Rowena broke the spell by reciting "Desiste, Adlevo onus tuum" (Stop, lift your burden) to Castiel. He shook violently, and fell to the ground. After that, the spell was revoked permanently from him without any adverse effect.