Time Lord Mind

''Vampire'' is simply a generic label for entities that absorb energy. Many many spirits have vampiric aspects, humans can vampirize(whether consciously or unconsciously). Summoning a vampire to do your bidding, does not mean going to a cemetery, performing some blood rite and having a pale man come to you and offer to drink the blood of all your enemies.

However, it is perfectly plausible to summon a spirit of the dead, and bid it go out into the world, and drain the chi of your enemies, even bring it to you. And this entity need not be a spirit of the deceased. It can even be a well-known entity like Lilith, provided you ask her nicely and she agrees.

''Werewolf'' is another term for anyone who assumes a canine beastly form in the astral. This intersects with vampires, and most werewolves are also vampires. Loss of control and lunar influence are both things that happen when working with certain vampiric entities, especially Qlipphotic ones. In essence, this is a werewolf. Just on the astral plane.

''Summoning the Doctor'' is perfectly plausible, though not realistic. You can summon the Doctor, as an egregore. An egregore, being an entity fueled by the minds of Whovians around the world, who has taken the properties of the Doctor.

Merfolk, once again spirits. Depends on how you classify them, though. A friend of mine referred to them as the jinn of the sea, but in my experience most merfolk are a variation of fairies. Still, there are undines, water elementals who are mermaid-esque. Becoming one, in spirit, means either merging with one, or integrating water on a deep level into your life. It will not grant you a fish tail however...

If you do summon the Doctor, go into his TARDIS and travel in time, know that:
1. Time travel on the astral plane isn't that special. Because there is no ''time'' per say in the astral binding you, you can easily step into the past or future while astral projecting, without the Doctor.

2. The Doctor, and the TARDIS you were traveling in were both imaginary. Doesn't mean your experiences were not real, or valid, it just means that the entities were egregores. And you probably entered the ritual with that knowledge in mind, so have fun!