Unfortunately, he doesn't need a pet to help him guard a place. What he needs is a plant that he can take with him to the many worlds that he will invade in the future.
He also needs a plant that can eat anything that they encounter on those worlds. These have put the Blood Vine out of the running.
In order to make a good decision, he used Aries as an example and considered how well the three plants would do in Aries. He compared the pros and cons of all of them in Aries.
After thinking about it, he realized that he would not be able to take the blood vine there to provide him with the life force that could save his life in times of need. So the Blood Vine will be useless in Aries.
Even if he managed to bring the blood vine to Aries, he won't be able to feed the blood vine with his blood because of the lack of mana, and he won't be able to feed the blood vine with the blood of the Vulcans and Tundras either, because their blood is too hot and cold.
