From information you give - I don't see this dream dangerous, he did not attack, you didn't say that you felt his anger, only his power.
The worst scenario - this was a warning, but if you say - you did nothing in real life, and you happy and comfortable, so I can't propose it.
Maybe in your magic studies you started new subject or learned new skill - that's why new power came across.. maybe this is your new familiar..
Maybe there is some uncertainty in your real life, maybe you have to chose new job with new powerful boss or travel some places abroad to study - then it means you are scared of unknown...
As I said - for complete strangers it is very hard to tell.
Sometime dreams have meanings, sometime they are nightmares and sometime they just bring our subconscious feelings..
So your saying it could be like my minds interpretation of receiving new power? you think a familiar could be suck a creature? The most I remember was the feeling of the presents of it, even before it locked eyes.
I misspoke, but yes I was analyzing my life to it. But I don't see any confrontation in my life, nor mystery of someone new. The coming of power is a possibility, but what you said about it not being about me. There was suck a strong feeling directed at me I had not considered my sleeping cousin as the target.
If, lets say - IF your cousin was the target, and you acted as his guardian - then - yes - creatures attention at first would be on you.
You can do some protection rituals for your cousin, just in case. Maybe wait for a few days and look for other signs.. try some meditation to look for an answer..
Going deeper - triangular shape tail means - "door". (To dream of a door represents access, new opportunities, and changes. It may also reflect an available option. A chance to do something different. A door can also symbolize a transition from one stage of your life to another.) And you said - you even opened cars door. This sign is repeated in dream and you should pay attention.
Maybe if your cousin is in any hardships, and you are trying to help him, this dream represent, that you feel new danger coming towards him and trying to protect him, that's why you were so desperate to wake him up and get him into the car...
This interpretation is based on my guesses - listen to your heart and don't take my words for granted.
based on description i can see, i believe the spirit wants to show you something, but you may angered it and it shut off the session, if you see the spirit in your dreams, be peaceful, confidant, and follow the spirit to show you what it wants you to see