5 Colour Commander Stand-ins
Some of the great things about Commander as a format are the restrictions built into the rules of the game. One hundred cards, singleton, but one of the most restrictive and yet creativity boosting rules is the Commander Colour Identity, or Rule 3 if you want to get technical.
The rules states:
A card's colour identity is its colour plus the colour of any mana symbols in the card's rules text. A card's colour identity is established before the game begins, and cannot be changed by game effects.
Cards in a deck may not have any colours in their color identity which are not shared with the commander of the deck. (The identity of each card in the deck must be a subset of the Commander's)
If you've been playing Commander for a while you are obviously pretty familiar with this rule as it is one of the pillars of the format and defines Commander in many ways. However if you've been playing for a bit, you're also probably aware of the DIY work-around to this rule – Five Colour Commanders.
I'm not talking about taking Atogatog and building 5-colour Atog tribal or making a Sliver Queen sliver deck. I'm talking about building a deck around a strategy that another commander might normally use but then applying 5 colours to it. 5 Colour Mayael the Anima or 5 Colour Animar, are some examples of this.
Of course if you choose one of the 12 WUBRG (+ General Tazri makes 13) commanders, you gain all the strengths of your adopted colours without the restrictions the original commander may have imposed. However, you lose mana consistency as well as the presence of your trusty general sitting in the command zone. In a 5-colour Marchesa, the Black Rose deck you better make sure you can get Marchesa out and then protect her or else your entire strategy could be lost.
So let's look at a few possible strategies and decks that might benefit from the 5 colour treatment and what WUBRG legendaries might actually work very well in the decks.
One note before we start: if you're building any 5 colour deck where the real commander is hidden in the 99, tutors are your best friend. Demonic Tutor, Diabolic Tutor and Worldly Tutor are some that immediately spring to mind but don't overlook the lesser known Time of Need, Eladamri's Call or even something like Fierce Empath if your commander's CMC is big enough.
5 Colour Marchesa, the Black Rose
Colours you gain: White & Green
The advantages you gain by adding green and white to Marchesa's already powerful strategy are plentiful. Aside from the obvious ramp and colour fixing green offers every WUBRG deck, with white in your deck, you get a lot of affordable board wipe spells that will decimate your opponents creatures while simply fueling your endless cycle of recurring your own. The wrath spells in Marchesa are already super powerful that when you make them cost 4 mana you give a lot of flexibility to a powerful control strategy. The other big gain that you get from a 5 colour Marchesa strategy is green's +1/+1 counters. I'm not even talking about Doubling Season since that card is actually fairly redundant in this deck, but instead I'm talking about all the Simic graft creatures that original Ravnica block gave us. Not to mention the evolve cards from Return to Ravnica. Getting counters on your creatures with Marchesa is one of the main goals and when you add green you make it stupid easy to do.
Advantages you gain: White board wipes, green +1/+1 counter cards, ramp & fixing, artifact & enchantment destruction
WUBRG General: Child of Alara
5 Colour Marath, Will of the Wild
Colours you gain: Blue & Black
Marath is another powerful commander in their own right but when you add the Dimir part of the colour pie, you open up a different set of strategies on the more controlling side of things. Obviously blue brings with it a slew of counterspells and black brings fantastic spot removal, but black also brings the ability to more consistently give Marath deathtouch with Sultai Runemark and Aspect of Gorgon, turning it into a machine gun creature killer. Add in some cards like Phyresis, Glistening Oil and even Corrupted Conscience and all you need is a big enough Marath and the Mana to kill someone with infect.
Advantages: Blue +1/+1 strategies (ie graft & proliferate), counterspells, black deathtouch, black & blue infect auras.
WUBRG General: Horde of Notions
5 Colour Daxos the Returned
Colours you gain: Blue, Red, Green.
Making a two colour commander into a 5 colour deck seems to be less of a popular strategy but if anything, you have more to gain than if using a 3 colour general. Daxos already fits quite nicely in Orzhov's enchantment theme but adding 3 more colours definitely gives the deck an interesting boost. There are a surprising amount of great cheap green and blue auras and enchantments that Daxos would love to get his hands on. I'm specifically thinking of cards like Curiosity, Rancor and Spider Umbra. There's also the Selesnya's propensity for populating Daxos' spirit token friends with Trostani and the always devastating Doubling Season or Parallel Lives, both which just happen to be enchantments.
Advantages: Ramp & fixing, blue & green cheap auras. Green token doubling & populating. Crazy blue enchantments.
WUBRG General: General Tazri
5 Colour Riku of Two Reflections
Colours you gain: White, Black
Riku's gains are pretty easy to spot when you switch him into a 5 colour deck – more spells to double and more creatures to spam. Specifically creatures and spells that interact with the graveyard become a viable strategy not to mention the host of big ETB effects that white's creatures offer. When you can double them up, creatures like Sepulchral Primordial and Angel of Serenity get out of control quickly. When you add Orzhov to Riku he also gains one of the most important abilities in EDH, in board wipes. You may not need to double an End Hostilities to make it effective, but just having wraths like it in your deck fills a massive hole that plagues Temur as a colour combo.
Advantages: Board wipes, spot removal, flickering, graveyard recursion doubling with Riku, white huge ETB abilities.
WUBRG General: General Tazri[c] (allies work very well with Riku)
5 Colour Brion Stoutarm
Colours you gain: Blue, Black, Green
Brion Stoutarm isn't exactly a super popular commander, but maybe that's because of the colour pairing he sits in. We all know the challenges Boros decks face in commander so why not forget about all that by just adding the remainder of the missing colours? Brion is the most interesting Boros commander and he only gets better when you add big dummies like [c]Worldspine Wurm or Ghoultree and with all the sacrificing you're doing it seems like tossing in a Palace Siege could get pretty nuts.
Advantages: Graveyard recursion, life draining effects, other sac outlets, big green creatures, ramp, fixing and card draw.
WUBRG General: Progenitus
So is it worth it to sacrifice the consistency of having your commander always available vs having access to the extra colours? When using this strategy just make sure you pick a “commander” that your deck can work without and perhaps even has some cards that do the same thing. Including these cards will ensure your deck runs smoothly and offer up a nice backup plan in case things don't go your way.