Hybrid warning message and rattling noise. Please help

i would really like some advice on an issue I have had.

My 2012 prius started to lose power on the highway and the accelerator stopped working. Alongside this, I got the hybrid warning message and to pull over in a safe place. After a while, the 12V battery died out too. I was towed home and the following morning I managed to get the battery recharged by a battery pack. The car would briefly drive before the message returned and I was unable to go into drive. In addition there was a rattling noise from the engine (see video)

What could this be? I am getting all kinds of different messages from garages. I would really appreciate your help.

 

I am unable to post a video but its the exact same the one one this reddit thread :

 

Thanks for replying my friend, 213000 miles and yes car has started burning more oil in the last year or so. However, levels are ok at the minute. I called AA (mechanics) and on their machine, the only code came out for a throttle body. However, the mechanic also said that a throttle body should not make this noise.
From calling around, other mechanics have said it may be the water pump, clutch etc. I am not very experienced when it comes to cars so I am grateful for all the advice I will get here! Thanks

 

Someone who came to see the car believes it is either the water pump or the whole engine. I will get someone to have a look at it soon. I have had people saying it could be a number of things but I am just worried about people charging me a lot when it is something like a cleaning issue.

There is no link for the thread, please let me know that would be helpful