And into this unusual jungle environment (which is a wonder of design -- both minimal in its suggestions (this isn't the same style as the overcrowded, lush jungle in Planet of Evil) and yet with curious details such as the tubing-like vines that make this place look satisfyingly alien), the TARDIS materializes and the Doctor steps out to break the fourth wall, turning the audience into his companion -- it's a really odd moment, to be honest, and is a much better argument for the Doctor needing a companion than The Deadly Assassin was -- as well as being the first really obvious moment of Tom Baker being indulgent with the role (something which will create issues down the line).
But this is the exception to this story rather than the rule; for the most part these two episodes are smart and engaging, and it's not long after this moment that the Doctor encounters Leela, who immediately identifies the Doctor as "the Evil One" -- which means that, for this tribe, the Doctor is the eponymous face of evil -- a clever move. There's also the matter of invisible monsters which the Doctor deduces must therefore be blind and will react to sound and vibrations: another smart decision from Chris Boucher's debut Who script. There are lots of nice touches like this; the Doctor's examination of the abandoned technology and the conclusions he draws from both it and the Sevateem's ceremonial gestures ("That gesture you did. ... It's presumably to ward off evil. It's interesting because it's also the sequence for checking the seals on a Starfall Seven spacesuit. And what makes that particularly interesting is that you don't know what a Starfall Seven spacesuit is, do you?") are really nice, and there's clearly been a great deal of thought devoted to the set design and the costumes of the Sevateem. The best part, though, is how the voice of the Sevateem's god, Xoanon -- who we can hear speaking to the Sevateem's shaman Neeva -- is recognizably Tom Baker's. And then, not long after, we get the fabulous cliffhanger of the Doctor gazing at the giant carving of the Evil One's face in the cliffside, which is clearly the Doctor's face -- so there's another, more obvious face of evil as well.
The second part continues this trend, with more explorations of the Sevateem's culture and speculation on what's going on with Xoanon and the Sevateem -- the most striking aspect being the appearance of the invisible monsters, which are screaming Tom Baker faces. There's a bit of plot advancement, but most of this episode is a fascinating exercise in world building, expanding on what we've already learned. There's also a really nice moment where Leela proves her value to the Doctor after the Doctor realizes he can't get past the wall next to the Sevateem village, as it's separated by an impenetrable time barrier (yet another lovely concept): "You know you said nothing could get within that barrier? ... Not light or anything. ... But Xoanon is inside it. ... How do we hear his voice?"
The other part worth remarking on is the Doctor's undergoing the test of the Horda -- the Horda being vicious piranha-like creatures. The Doctor proves his worth fairly easily, but what's curious is how he casually flicks a Horda onto the shoulder of the Sevateem who slaps Leela -- it's a surprisingly callous moment, even if it seems to be done out of a fit of pique. Still, it only lands on his clothes rather than bare skin, and maybe we can be generous and acknowledge that the Doctor knew this would only scare him, rather than kill.
Odd cliffhanger, though, as one of the Sevateem, Tomas, is threatened by an invisible Tom Baker face. Apparently we're supposed to care more about the Sevateem than we actually do...