Becoming a Druid means you've been ordained as the spiritual representative of some particular tribe - the one you performed the outcast initiation ritual with. Over the night after you ate the heart, you commune with their gods and gain a spiritual affinity for the type of environment they live in.

Pick an environment. (Ideally, the one you and your tribe normally live in).  You can make up d8+wis things about it, now or later. The DM has to roll with whatever you say, within reason. See below for some examples.

Your relationship your tribe is a Gandalf deal. They'll be cool with it if you disappear for long periods of time, then show up at random years later; Outcasts are mostly loners anyway. Likewise, they aren't sworn to follow you or anything, but they'll generally help you out. You may have to work to earn their trust, and if you act against them, their gods, or their ideals, they might kick you out of the druid rank and force you to become an outcast again.

Your biggest responsibility is to represent them in the spirit realm and act as their psychopomp. That'll mostly happen in dreams. You can assume that you're spending a decent amount of time between sessions ferrying babies out of that great undiscovered country, ferrying dead souls back in, and bargaining with various petty gods for the benefit of the tribe.
  1. You get an extra attack per round. Divide your normal attack bonus however you like between attacks.
  2. You get +2 to hit in a specific situation. For example: Unarmed combat, from horseback, at long range, while drunk, when you're above the enemy.
  3. If you roll max damage with a bow, the arrow goes wherever you want. Hand, eye, knocks their weapon out of their hand and then ricochets into another guy, etc. 
  4. +2 to stealth, bushcraft, or sneak attack. Your choice.
  5. Pick an animal. If you kill it and skin it, you can wear its skin as a cloak to become it once per day. Lasts one hour. If you pick a weird fantasy animal, you'll need to save vs. magic whenever you wear it, to avoid going crazy and being trapped in that form. -2 or -4 penalty to the save for ultra powerful creatures.
  6. You're getting tainted with the essence of the old gods. Permanently acquire one mutation feature (bear claws, fish gills, bird wings, etc).
  7. You've learned astral projection. Get the right herbs, prepare them right, and go into a trance. You can walk invisibly through the world, fly and pass through objects. Beware, dangerous things lurk in this invisible space. First time you roll this, you get ten minutes. Second, you get twenty minutes, and you can fuck with people's dreams and their minds. Third, you get half an hour, and you can communicate with the ancient creatures that move through the astral plane.
  8. You can command a level 3 spirit from the summoner table. You have to roll 16 or better with d20+wis+level to order it around, just like the summoner does.
  9. Once per day, you can prepare a sacrificial lamb. Get one living animal, any kind, and scratch a bunch of runes on it. You can force one poison or illness out of someone else, and into it. Anyone who eats the animal, or is bitten by it, will be inflicted with the ailment. For especially serious illnesses/poisons, you'll need to roll a save to avoid just splattering infection over everybody. Every time you re-roll this, you can pack one more infection into your lambs.
  10. nature speak, speak with plants, rocks, etc
  11. You've got a cool familiar. Giant wolf, eagle, turtle, whatever. Add their hit points to yours, you can go into a trance to become one with their mind and play as them. Every time you re-roll this, they learn some cool power.
  12. You can effect the weather once per day.
    1. Water. You can summon rain and make rivers flood or slow to a trickle. You have to draw on moisture that already exists. This will be much harder or impossible in dry, desert environments.
    2. Clouds.You can make clouds cover the sun, fog rise up to conceal the party, or part snow, rain and mist.
    3. Fire. Calm volcanoes or make them erupt, stop or start raging bushfires.
    4. Earth. Crack it apart, make it shake, etc.
  13. Herbs, poisons and drugs!
    1. You've got access to something that all the nobles are hooked on. There's a 1/6 chance any normal person will be addicted to it, 1/4 chance that a noble is hooked.
    2. The black plague. 
    3. Makes the victim super susceptible to suggestions. 
    4. Blinds. You have an antidote, which makes people invulnerable to it. Obviously, you can burn it to make blinding smoke.
  14. Sacrifice some dudes on a black altar to gain knowledge and assistance from the old gods. Every time you roll this, you can ask them for a single piece of great knowledge: The location of some incredible whatsit, a great spell, etc.
  15. Pick a normal, non-sapient animal. These guys always obey and understand you. You can give out a call that will bring any of them that are close by to you, and you understand what they're saying at a basic level.
  16. Haruspex. You can read the future in the patterns made by animal guts. Once per day, you can kill an animal and examine it over half an hour to get the answers to d4+wis questions about the future out of it. Roll this again and it's d6, d8, etc. The better the animal, the more clear and useful the visions will be.
  17. Once per day, you can make a talisman dedicated to some local spirit. The talisman gives you a d6 to add to one roll that comes under it's spiritual jurisdiction. For example, you might pray to a snake god for protection from poison, and a sea god for safe passage. These are small spirits, so they only have power in a small environment: leave the place, and they won't be able to help you.
  18. You know a ritual. You can do it once per day, and it takes half an hour. Gather a bunch of people up, ceremonially slaughter an enemy, and then have them all eat its heart. The ensuing righteous bloodlust gives them some of that enemy's strength and abilities for an hour. Everyone must eat at least a quarter of the heart, so if you want to do it for more than 4 people you'll need to slaughter more of the same enemy, all at the same time.
  19. You have gained knowledge of another environment. Pick a place, and you can make up 2d4+wis things about it. You can use them all now, or wait until it's crucial. You can also use this for a type of place instead of somewhere specific: For example, any arctic waste, desert, ruined city, etc.
  20. Roll again. You get that effect, but twice as good.
Here's some examples of what you might want to do with this environment-determining stuff.

-Draw something on the map. A secret underground river that goes underneath the goblin fortress, an oasis in the desert, a path through the mountains.
-"This is the hunting ground of the Bloat Ghosts. If we piss all over ourselves, they shouldn't be able to smell us."
-"Luckily, the Sarkassian blood ant has a crippling weakness to copper. Empty your coin-purses!"
-"Don't drink the water. It's tainted with the hallucinogenic seeds of the Muluwe plant."
-"Wait... I know this bear... yes, this is the very beast I fought ten years ago..."

The only limit on this ability is that you can't be boring (which is the secret limit on every ability).

The Paper Trail

So much history here. Here's a few particular points of interest:

Only Gilgamesh is fit to rule, mongrels!

Party A, traveling through the Babylon district, was sucked into the monthly lottery which determines the fate of all who live there. You become a slave, a noble, a brick wall, all based on your result in the lottery. I decided to have them all roll d20's to see how good or bad their fates would be.

Three people rolled a natural twenty.

One of them was Shenks, a gremlin played by Matt Rundle. He became mayor of the district, and built this tower.

He lived pretty high until the party B lead a peasant rebellion against him, burnt down the tower and installed one of their own as mayor: Gilgamesh.

Another lottery winner became the leader of Cell Apeiron, a bunch of revolutionaries which conspire against the lord regent from this hidden base. Matt fled here to languish in the sewers as the Under-mayor.

From here, party A sent out shadowy assassins, who succeeded in destroying Gilgamesh by hurling him into a black lake to be torn apart by the tentacled horrors within.*

Magic = Haywire

While the party was travelling through here to kill the Lake Dragon, I rolled an encounter. The result - the magic in this part of the district is strange, twisted - spells will have crazy, exaggerated effects. A wizard decided to try a LotFP summon spell. He rolled a natural twenty.

To those who haven't seen the lotfp summon spell, this is game-breaking. You have to roll on another sub-table, and each result could have apocalyptic consequences. The one we rolled: The DM becomes a PC, and a random PC is chosen to DM.

We went with it, and it was a blast. We rotated through three DM's for a few weeks, each one adding their own shit to my world. I loved it.

Dwarf Invasion: Added by one of my DM's. According to them, Vornheim used to be a dwarven city, and ancient tunnels still lead up into the home of every man, woman and child. The dwarves lurk there, watching the city, preparing for their chance to take back what's theirs. 

Glove Towers: Born to a fallen house in the Ghost District, the lady of the glove goes around pretending to be offended by people so she can challenge them to a duel. By defeating numerous nobles, she is slowly increasing the size of her land.

Trail of Destruction: Some giant demon is moving through the city, leaving this trail behind it. As you get closer the sunlight dims, a black rain begins to fall, and the streets are deserted except for ragged warbands of clerics rushing back and forth trying to evacuate the survivors.

Beware of Worms: A big portion of the elf district has been walled off after the prisoners in the tower were released along with a shitload of death worms. Perhaps they've constructed their own worm-prisoner society behind the barricades - who knows? None who go there return.

---Do not cross this line if you are a player.---

Eshgriel (who has four levels in fighter): Too funny to pass unremarked. Party B got hold of a massive haul of purple lotus power as they were escaping the prison. "You know that this powder may give you the powers of a god... or destroy you utterly." Of course, they decided to snort it immediately. 

The first person to snort it died. Prison guards started hammering on the door. A second person snorted it, and died. A death worm started coming up the corridor, the guards were breaking through. Everyone egged on a third person, who snorted it... and died.

So, later, they're the house of Eshgriel the medusa. Half of them are turned to stone, one's poisoned, the Plasma Ghoul is gnawing on another and all the dogs are dead except one - a Busking Dog. As a last-ditch effort, they hurl the powder at Eshgriel - who gains four levels in fighter.

Despairing, the last PC and Busking Dog try for a suicide pact, and snort the last bit of Purple Lotus powder. The Busking dog gets one result: Wants to move overseas to marry. He flips out the door, en-route to a tropical beach.

*This is a lie. In reality, the dead man was a homeless hobbit, dressed up to look like Gilgamesh.