Modern Maul: Was He Fully Trained?
There's plenty of older Legends sources, Book of Sith from 2013 being most recent, claiming Sidious kept some cards to his chest while training Maul. That Maul had a very specific purpose - to kill Jedi and perform missions in the shadows for Sidious - and to be honest and frank, yes, this was the original 2000s inception of his character. Used up and spat out, Boba Fett style. And yes, it makes it very hard to resurrect such a character after you've cut him in half and start doing new things with him, especially in the narrow creative framework that is TCW; the short time between AotC and RotS wherein, at best, some supplementary events for the movies and unique stories can take place, but nothing to change the main storyline of Star Wars.
With that said, I can't help but notice the overwhelming evidence from all more modern sources that Maul's training was not particularly specialised; in fact, some of these sources go as far as to say that Maul's training was nothing short of the best Sidious could offer. I think it's self-evident from TCW, what with manufacturing a micro-RoT plotline with Savage/shadowy power base out of virtual thin air, that Maul's character took a permanent deviation from the original concept. Instead of an incredibly lethal weapon and nothing else, we have additionally a fully fledged, manipulative, cunning and adept Sith Lord.
I'll start with a few observations and points.
1. Relatively recent canon sourcebooks, such as Ultimate Star Wars, echo from a decade old Fact File and other sources that Maul is "one of the most highly trained Sith Lords" or "apprentices in Sith history." As well most dangerous, lethal, skilled etc. While this doesn't conclude my point by itself, it's certainly not suggesting the reverse. It's a step in the right direction.
2. People see a lack of Force Lightning as some huge detriment. Whether we'll get a real answer on why Maul doesn't use it, we'll never know. It is true that among canon Sith Lords, he's the only one who doesn't have an excuse for not using it (Vader and his suit). Instead of speculating on why that is, I'm going to go ahead and say it's just not relevant. Is it a useful tool to have in your arsenal? You betcha. Does it prevent me from making my argument? Apparently not, as my evidence below will hopefully suggest. Remember that it is the construct of fans, not creators, that Force Lightning is a necessity to be considered a fully trained Sith Lord. For all we know, Maul can't use it for genetic reasons, or something equally stupid.
3. A question I would pose to people is this: what motive could Sidious have had to train an apprentice who is sub-par? One of the primary Sith directives is to kill the Jedi, in order to wrest power from them and dominate the galaxy. If nothing else, regardless of the obvious manipulative, psychological and political talents Maul now has, Maul was evidently trained to be as good at killing Jedi as possible. Perhaps Sidious did leave something out of Maul's training - it's evident he doesn't tell everyone everything. But why would he restrict knowledge that helps Maul fulfil the primary directive of the Sith? A point that is inevitably raised is what Sidious said to Plagueis in Darth Plagueis, regarding Maul not being a true Sith Lord, but rather a tool for their own purposes. But apparently those who raise the point did not read, forgot or ignored the later parts of the book wherein Sidious muses his double life of being both a master and an apprentice, or where Plagueis gleans a father-son-esque relationship between the two, or where Sidious gloats over a dying Plagueis that him and Maul will be fulfilling the grand plan without him. Clearly, telling the guy you want to learn everything from that you are fully intent on replacing him once you have is a nonsensical thing for Sidious to do, and the book demonstrates this well, even if it's gone over more heads than every american football in history.
With that out the way, let's get to the evidence. I know variety is the spice of life here on KMC; anything from the most obscure Legends sources on the backs of Embo bath salts to the highest authority of canon is worthy of consideration depending on the debater, so, I'll put them in categories. Note I haven't included every scrap of evidence for the point I could ever muster, just things I've held onto and others I discovered today.
Dave Filoni, Sam Witwer and by proxy George Lucas
Dave being the director of the episodes in which Maul is resurrected suggests to me he might know what he’s talking about regarding Maul’s new character. Sam was heavily involved with the creative process, which makes sense since he had to become Darth Maul - Dave has said he has taken ideas from Sam for Maul, and is happy to leave him to speak freely about Maul during heavily populated Q&As, while sitting next to him. And the kicker is that every decision for these Maul episodes went straight through Lucas. In fact, it was Lucas’ idea in the first place that Maul go through this transformation. Him challenging Sidious in some manner, and establishing a power base in the crime underworld, was George’s idea (it was ironically also his idea to cut him in half).
So I take their word seriously if they aren’t expressing it as an opinion, but rather answering an enquiry that requires a specific answer. I know some do and some don’t.
Dave Filoni explains that Maul is trained in “all types of Sith ways”, not the least of which is manipulation, among heaps of other praise. You can see why I stopped giving a shit about lightning a while ago.
[After discussing the validity of Ventress and Savage’s claims to being considered Sith] Maul is a super dangerous threat because he has been trained for years. He’s really adept. So he’s kind of in the Vader-realm, and you know he, he’s a bit severed from what he knew which was having a master but he’s well trained by Sidious in all types of Sith ways. Not the least of which is manipulation. Again, I don’t want to give too much away... [so clearly this isn’t an opinion if he’s giving us something factual but “doesn’t want to give too” many facts away]
https://youtu.be/Mr-6Lfkvxkk?t=2m38s
Next, one of the most beautiful things I’ve ever heard come from Filoni’s mouth: Maul was trained in Sidious’ likeness.
[The interviewer gets done discussing how Maul seems far more calculating, intelligent, no longer just a living breathing weapon devoid of thought etc compared to his TPM self]”Yeah I think the root of all that thought is that if he is a good apprentice to Sidious he needs to train him in his likeness really, and he teach him what he knows. Sith by their nature can’t be so overt. He is a deadly weapon cause George needed him to be that in The Phantom Menace, but he didn’t have the time to get into more who he is. If you listen to the few times he speaks, he is very subservient and he doesn’t come across as someone who is very dim. He comes across really rather sharp, which I think makes your villain that much more effective.”
https://youtu.be/RGvwH4Z92A0?t=56s
Now I could get into Witwer, but I’m thinking that’s sufficient for the point. Witwer says nothing Filoni hasn’t already stated overtly here.
Legends
So we already mentioned the plentiful sources describing Maul as “one of the most highly trained” Sith ever, but here’s something even more explicit to serve my point:
"A deadly combatant and powerful Sith Lord, Maul spent his entire life in servitude to the dark side of the Force. Taken from his home at a very early age by Darth Sidious, Maul was trained mercilessly in all forms of the Sith arts, becoming the living embodiment of evil."
I’m aware it’s a shit-tier source (hence why Ant found it), but the purpose of the source is to inform fans on the more subtle nuances of the characters. And, clearly, people buy them, so I’m not going to hypocritically dismiss it in favour of a Fact File, which functions identically for all intents and purposes.