Each of the factions have multiple benefits and disadvantages. For example, a Harper will argue that everyone is free to whatever they wish so long as they don’t harm another, while a member of the Lords Alliance will argue that we need rules and structure to keep people from destroying each other or pursuing selfish aims. The Zhent seems more like the Mafia to me, and the Silver Gauntlet is “good by any means necessary”. They could of made factions more important in Faerun but then retracted it, which was a shame. 

Then there’s Eberron which is more like caste systems and modern corporate oligarchy. Fascinating but thick 

Those seem like really powerful rewards for just joining an organisation.

They also seem really strange, mechanically. I mean, I shake hands with an Order of the Gauntlet representative and make a pledge, and now I have damage resistance on every single thing that hurts me?

In my POTA game, faction membership gives access to resources. Faction members can access cheap gear, consultation, and training. They can request backup from the faction. At a higher rank, they can command faction resources. Of course, the PCS are also themselves faction resources, so when other members call on them for help they are obliged to respond.

I've played in games where faction membership granted you what were essentially bonus feats or features at certain ranks, representing special training or resources. But I wouldn't hand out benefits just from signing up, until the character has a chance to have actually learned some new techniques or accessed some special equipment to justify the new feature. 

trivia-you'll notice a typo in the DMG though that hasn't been corrected...DMG has the faction as "Lord's Alliance" in the chart, but "Lords' Alliance" when you look at the picture with the faction symbols...everything else I've looked at is "Lords' Alliance".

Quote from HeathSmith >>

trivia-you'll notice a typo in the DMG though that hasn't been corrected...DMG has the faction as "Lord's Alliance" in the chart, but "Lords' Alliance" when you look at the picture with the faction symbols...everything else I've looked at is "Lords' Alliance".

 

Technically, Lords' Alliance would be correct, since it's the alliance belonging to all the Lords, not just to one Lord. 

To the OP, there are some ideas in the Acquisitions Inc book you might be able to build on for this sort of thing.

First, PCs have the opportunity to choose a "company position" (could be reskinned as a faction role) and get some mechanical benefits and some RP benefits from those positions, plus one magic item that gets more powerful as you progress through the tiers of play.

Second, the back of the book also has a section talking about "Iconic Faction Features" - so, NPCs belonging to each faction (in AcqInc, rival companies) get roughly one passive benefit and a couple of once-per-day abilities to boost them.

It's a good mechanical structure, and the framework can be reskinned and adapted to virtually any style of game. But it seems like not that many people know about it - I get the sense that some people kind of turn up their noses at the AcqInc book due to the style of humor...

Quote from Oisin >>

I really dislike the way factions are handled in 5th ed. They're there, but almost as an afterthought. They have ranks, but you gain nothing from pursuing those ranks. I decided I wanted to expand on that a bit. Of course, I'm stuck on a few things. I'm not sure if I've made things too unclear, (obviously what I want makes sense in my head, but if I present it to players, will it make sense to them?) Also, I'm stumped on what I should do for a lot of the rank 5 abilities. Any good ideas that fit the theme?

What I wanted was to make each faction unique and interesting, with abilities that matched the flavor of that faction. That flavor, at least in my head, is:

• Emerald Enclave - Protection of nature is the most important thing. All of their abilities involve the natural world.
• Harpers - The harpers are diplomats and peacemakers. They make great arbiters and value diplomacy over outright combat. Consequently, all of their abilities go to making them better diplomats.
• Lord's Alliance - The Alliance is all about nationalism, and bringing glory to the people of their town, nation, etc. So their abilities make them great leaders.
• Order of the Gauntlet - The order is all about protecting the little people. When there's defending that needs to be done, a Gauntlet is standing in front. Their abilities revolve around making sure their allies are safe.
• Zhentarim - Zhents are focused on merchantile pursuits. All of their abilities (with the exception of the snake, which I'm not fond of, but is so directly tied to the Zhentarim that I felt it HAD to be a feature) involves merchant pursuits and making money.

That being said, I've also limited it based on the Adventurer's league level limits. So, you need a specific amount of renown for each rank, plus you need to be level 5 for the third rank, level 11 for the fourth, and level 17 for the 5th. I'm trying to balance the benefits across each faction, but also make them useful for someone of that level.

So here's the benefits of each faction.

Emerald Enclave

1. Leaf Clasp - Gives pass without trace in natural environment, and advantage on stealth in the wilderness.
2. Knowledge of the Forest - Can identify any naturally occurring animals or plants
3. Immunities - Immune to natural poisons and venoms.
4. Woodwalk - Able to travel instantly between groves
5. ???

Harpers

1. Harper Pin - Gives disadvantage to attacks made against the harper with magical attacks. (once per turn)
2. Harper Knowledge - Gains proficiency bonus to any Intelligence checks, if already proficient, double the bonus.
3. Sanctuary - Sanctuary once per long rest, DC is 10+Harper Rank, + Charisma modifier
4. Tymora's Smile - Luck bonus - applies proficiency bonus to Armor Class
5. Mystra's Boon - Gains advantage for Saves against Magical Attacks

Lord's Alliance

1. Lord's Cloak - Applies Advantage to Charisma saves and checks
2. Man of the People - Able to sway public opinion in the Lord's favor (effectively move them one rank, depending on the lord's intention.)
3. Rally the Troops - Gains up to 10 followers to defend the Stingblade, and the area. Use Bandits stat block
4. Spirits of the Land - Able to call on the land's ancestors in battle. (In my head I see this like Aragorn and the spirits of the oathbreakers)
5. ???

Order of the Gauntlet

1. Damage Resistance - Subtract proficiency bonus from damage taken each round.
2. Taunt - Force opponent to attack you
3. Blade of Justice - Gain advantage to attack anyone who damaged you in the previous turn
4. Aura of Law - Anyone in 15 radius gains disadvantage when attacking Vindicator's allies
5. ???

Zhentarim

1. Snake Pet - flying snake
2. 10% discount - 10% discount on any purchase, and items sell for 10% more.
3. Cover Identity - Gains cover identities equal to the character's charisma modifier
4. 25% discount - 25% discount on any purchase, and items sell for 25% more.
5. ???

 

 Noted for future self reference.  Good stuff, I did something similar.

 here's a PWYW on dmsguild that attempts to weave together the AL season 10 rules, DMG rules, and M.T. Black's Darkhold, Secrets of the Zhentarim

https://www.dmsguild.com/product/306676/Guide-to-the-Five-Factions

i've recently become a big fan of minimizing discounts for Zhentarim agents - kinda makes no sense that a group of cutthroat murderers and thieves would be giving anyone wearing a winged snake a friends-n-family discount.

Quote from HeathSmith >>

 here's a PWYW on dmsguild that attempts to weave together the AL season 10 rules, DMG rules, and M.T. Black's Darkhold, Secrets of the Zhentarim 

 
With a cursory glance this looks interesting. I might incorporate it into my current game! (Although, this group is MUCH less focused on factions than the group I was running back in 2017 when I originally asked this question.