The Penalty wants to be a scary and disturbing story, and the illustrations do their best, but it is undermined by the fact that the entire narrative is about the Doctor having a nightmare while suffering from "Ponassan fever", as is made clear in the first paragraph when Nyssa and Tegan deliver the exposition to each other and to us reading. Hence we know that none of the dangers the Doctor faces are "real."
The Doctor turns on the Tardis scanner and hallucinates a lot of scary faces looking at him.
This is a pretty scary picture, although I know how to make it even scarier!
The Doctor's nightmare then changes so he is being threatened by the Thallisans,
thousands of deadly, robotic war-machines whose war-sirens sounded death!
They sound like a great monster, but what a pity that they aren't actually in this story. The same goes for the Dren,
heartless mutated reptiles with artificial minds who had come to earth to conquer it!The Doctor imagines them too, and then the "Omegans" who don't even get that much of a description.
The Doctor forgets who he is, and then he remembers, and then he is being chased. They catch up to him and he worries that he may regenerate:
The Doctor knew that he would not die. Knew that he could not die, not yet, not for so long. He knew that he would regenerate, return from death re-formed. Regeneration was both the gift and the curse of the Time Lords. The Doctor had felt the touch of death before, so many times before...
...and then the Doctor gets better. The pointlessness of this story (redeemed, in part, by the pictures) is encapsulated by the final paragraph, in which the title is explained:
Later, when the Doctor was finally preparing to dematerialise the Tardis from the surface of Ponassa, he pondered on what had happened to him. He had read somewhere of a theory that stated that whatever horrors a person meets in a nightmare, they are, in fact, only warped realisations of half-buried memories and experiences, magnified by imagination; fears and feelings that are ignored when awake but let loose when the body slumbers. He vaguely remembered someone describing nightmares as the penalty that has to be paid for enjoying an untroubled day and life-the more adventurous the life, the greater the penalty. The Doctor did not necessarily agree with the description, but it was at times like that that he regretted having adventures that stretched hundreds of years into the past and far into the future, because one thing was for sure: in the time just passed, his penalty had been collected.
I also have a theory. My theory is that this is utter nonsense.
It is time for sleeps now, bye bye. Zzzzz.