He's quite an interesting companion. Certainly not a standard template. First of all he's visibly not human, which is something the show still hasn't done. But then the constant make-up would be expensive and time consuming. It also creates an issue whenever you do a modern day or history based story, as everyone first has to react to the alien walking around with the Doctor before we get on with things. It could be interesting for half a season, but after that it would just get in the way.
Big Finish got round this problem to start with by having C'rizz's first season in his home dimension. Upon returning to the Doctor and Charley's universe it did get in the way a few times. People finding the strange lizard boy weird. But it was also here that C'rizz's actual character started to shine.
When we first met him back in The Creed of the Kromon we, and the Doctor, were told that there was more to C'rizz than there first appeared. It wasn't really dealt with again until the finale of the Divergent Universe saga The Next Life where we find out that before he met the Doctor he was a bit of a serial killer. A Church sanctioned one anyway. It was classed as 'saving', but he wasn't overly keen since he gave it up to be with the woman he loved. Who he then killed. To save her, mind.
This history was left unbeknownst to the Doctor, but his second season was spent with ever threatening behaviour, and the appearance that his 'saving' might be even worse then just killing them. Something like he absorbed their personalities as they died. This was bypassed for a less thrilling conclusion. And unfortunately the same goes for the character as well.
Most of the above is ignored for his finale. His personality absorbing is strangely turned into full blown psychic powers, and the religion aspect is picked up on, sort of. Rather than anything with the Church of Foundation we get general Hell beings and a war on a planet that has suffered a weird extinction event where everyone stopped ageing. In the centuries that have passed the majority of people also have forgotten technology and turned religious. None of it makes a great deal of sense, and the lack of addressing any of C'rizz's long running plots really ruined the whole affair. He might sacrifice himself just to save the planet, but that doesn't make for good storytelling. So much more could have been done with him.
The unstuck from time was a nice idea, as was the fact that this group of scientists over the course of centuries they now lived, left behind the science that had trapped them and turned to some made up religion. Though the execution, and the attempt to wrap C'rizz into it left Absolution lacking.
Sadly the same can be said for C'rizz on the whole. Big Finish clearly tried something very different with him. There's a lot of good ideas bubbling under the surface. They just never fully form. Maybe it was the constant changing of Big Finish's plans, pulling out of the Divergent Universe long before they had originally planned, and then deciding to just restart the Eighth Doctor all together with Lucie Miller. I'd like to think the C'rizz was a victim of bad timing, because the idea behind him shows far more potential than we ever get to see.
Charley's departure from Eight is up next. Hopefully she fares better.