How to load a view for the error page?

[eluser]Aquillyne[/eluser]
[quote author="inparo" date="1216514906"]Whenever CI encounters an error it calls the proper function in the Exceptions class.[/quote]

How early on is this? Is CI itself instantiated at the time?

In the MY_Exceptions class, can I, for instance, use, "$this->session->set_userdata()"? Or if not (as I imagine is true), how might this be possible? I suppose I might have to get_instance() CI?