Roughly paraphrased from something that Eris said...
That got me thinking. Eris is one of the only few characters that comments on the things that you have done, which is the only thing similar to the "persistent world" that was promised with Destiny.

As it stands, there is very little that changes when you begin your story, and pretty much nothing has really changed in the world since the game came out (besides the Loot Cave ashes)...

What if there was a new event that would happen to your character after the Crota kill? Her quote about minions hunting for you sounds really cool, and could be implemented fairly easily.

In a different game that I play, there are a number of enemies that can come after you in this manner, from annoying, to challenging, to downright terrifying (one trio of enemies that can hunt you and your team cause you to instantly fail your mission, and greatly weaken your character for 24 hours in real-time. Another enemy captures you, separates you from your group, and imprisons you, requiring you to do a mission where you escape from containment without your weapons before you can continue), and the encounters are always preceded by flickering lights and ominous comm transmissions.
The neat thing is that these special enemies come with unique rewards that make you want to stand your ground, if you or your team is up to the challenge...
Think of the Hand of Crota Thrall that is near the Skywatch. It's not in a Public area. It's in a closed-off loading zone that only you and your fireteam can encounter... So what if there was a chance that a special type of Hive could hunt you down when you ventured into one of these areas?

I'm reminded of Urzok, which is an extremely powerful enemy that you can't usually take on your own, but you have to at some point, so it benefits you to bring a team...
What if something similar happened, and you had to bring your team to help you?

So picture this:

You're doing the patrol missions in the Cosmodrome, and as you head up to the Skywatch from the forgotten shore, you begin to hear whispers, and the lights go out.

*A Dark force has found you*

Thralls start to pour out from the spawn zones, and you fend them off (earning plenty of glimmer if you remembered to activate a Wax) for a minute. This gives your fireteam time to get to you, because you're going to need the help (or it gives you time to flee if you're not up to the task).
As the third wave of Thrall spawn, there are whispers around the area, and it becomes a Darkness Zone (Restricted Respawns).

*A Hunter of Crota comes to avenge his master*

And then it darts from the shadows- a Defiled Hunter (Level 32).

Credit where due.

Now you fight a really fast melee-focused enemy that can dart to and from the shadows, and only your Ghost lights and Muzzle flashes cut through the darkness.

Attacks:

• (Full Health)
  Melee Rush- Similar to Fallen captains, the enemy rushes out to deliver a quick flurry of melee attacks against one or more targets. He moves much faster than other enemies, so while the attacks don't do as much damage, they can quickly stack, and seven hits will kill a Guardian with max Armor rating. He can also quickly leap up and hit airborn Guardians for double damage, so agility and mobility is important (he has no shield, so while avoiding him is advisable, he is completely exposed during this portion of the fight, allowing non-targeted Guardians to focus on shooting him).
  360 Slash- If he lands five melee hits during the Melee Rush, he will roar and quickly lunge towards the second-closest target and deliver a radial slash that affects all targets around his landing spot (While the attack can instantly kill a Guardian, ducking/sliding/Jumping can avoid this attack entirely. Being aware of your positioning is key to anticipate this attack).
  Thrall Wave- At every seventh chunk of health lost, he will dart back into darkness and summon a wave of Thrall (and cursed Thrall) from nearby spawn rooms (and the ground), which will occasionally accompany a second attack from him. (Raid gear, and gear that spawns extra orbs can be extremely useful during this wave, letting you spawn Orbs for your teammates).
  Blinding Vestige- Right before attacking, or during a Thrall wave, he will summon a Vestige under a random Guardian. While this Vestige does much less damage than a Wizard's, it causes a stun effect similar to a Flashbang, momentarily blinding nearby Guardians. (Sticking too close together is a sure way to blind the entire group, so splitting up is advisable).
  
  
• (Half Health)
  Once his health gets below half, he'll know that you're a threat, and focus on more Defense-based variants of his moves. He'll let out a shriek to let you know you've reached the halfway point.
  
  Heavy Melee Rush- His Melee rush does much more damage (three hits will Kill a Guardian at full health), but he strikes slower, and no longer follows up with a 360 Slash.
  Wall of Darkness- A wider version of the Knight's Wall of Darkness, he'll throw this up to his side when nearing a target, making him harder to hit from certain angles (Guardians will have to move or attack from above to hit him.
  Tackle- If he reaches a Guardian while throwing up his wall, he will pin him to the ground (throwing him into third person) and begin slashing at him if enough damage isn't done to him in five seconds, he will kill the Guardian (Any Grenade's initial impact, a Saint-14 Ward of Dawn, and Rockets will cancel the attack if he hasn't reached his target, and a direct Rocket hit will instantly break off the Tackle if he's already pinned a Guardian.
  360 Slash Strike- During a Thrall wave, he will roar, then leap from the shadows at a random Guardian, doing his 360 Slash attack (again, this can be ducked/slid under, or jumped above if you're quick enough).
  Multi-vestige- He'll throw up three random vestiges on the field that last a very short time (easy to avoid if airborn).
  Stream of Thrall- Scattered Thrall will spawn around the room during the last quarter of his health, making use of Rockets risky (beware the proximity detonation).
  

As it's a Darkness zone, respawns are restricted, so Alpha Lupi gear (and LBN) come in handy.

If he downs everyone, you get nothing from the encounter. Taking it a step further, maybe you're left with a fifteen-minute debuff that lowers your shield capacity by half, making the following PvE missions just a pinch more difficult (good luck with a public event on the Skywatch that you were headed to).

But if your team is successful, he might have drops like any strike boss. Legendary Engrams, Motes, Coins... Maybe even a chance at an Exotic.
Heck, he may have a chance at unique drops, like 5000 Glimmer, 10 Radiant Materials, an Exotic Shard, a custom Sparrow drive (Black smoky trail), unique shader (rust and grime), class item, Emblem, or a unique weapon...

Triggered:

Marked- Any player that has killed Crota gets "marked" for revenge. If you haven't killed Crota, being in a Fireteam that has will still allow you to participate and receive rewards (if you don't have TDB DLC, you won't get non-vanilla rewards), although you will be at a disadvantage if you're not ranked high enough (He's a 32, which gives some leverage). Marked players will receive a message from Eris at the Postmaster, telling them that she senses "A dark force being birthed in anger of what you've done". Three Marked players in a Fireteam have a higher chance of an encounter than a group with only one Marked person. (This not only entices players to get the DLC, but encourages players to run Crota Raids, as you will need to run a new one in order to receive a new Mark. It also helps explain why this Hive was not present before the fall of Crota).
Word Spreads- Doing Patrol missions on the moon and Cosmodrome increase the likelihood of an encounter, as information of your whereabouts and actions travels through the Hive's channels. (This promotes more population in Patrol, giving some Life to the lesser-visited areas, as people will now be running all types of Patrol missions, instead of skipping the non-killing ones).
Reset- After the encounter (whether successful or unsuccessful), the player loses his Mark, which means that he'll either have to run the Crota strike, or play with someone who has. This promotes getting groups together and running Crota's End more often, so LFG sites will benefit by getting more people together.

The entire encounter is great in that it brings a sense of dread and tension once you realize that he's coming for you. You get one shot to beat him (unless you run away, which lets you keep your Mark), so it's extremely satisfying when you succeed, and the rewards can make you really stand out, as it's a rare event to begin with.
It's also a Boss Battle that is unlike all other encounters (besides the fact that you can't entirely anticipate it), because it's more about communication, momentum, and skill than the other bullet-sponge bosses, and each class has perks that help them out in different ways. The entire encounter should last around five minutes, but can build a sense of camaraderie among a group in far less time than a Raid run.

Destiny needs more unexpected chunks of tension and fun.

This is an absolutely incredible encounter idea, and a PERFECT way to create a persistent game world for the people who have completed the raid. Holy hells, Korny, well done.

I really like this, Korny. It works within the confines of what's already built and established, but still provides something interesting, new, and fresh to it. Having it work as a sort of triggered public event also gives people who might be in the area a taste of what's coming. The chance for all to get some sort of loot would also be awesome.

That said, I think that there should be two different levels to this -- the first being defeating the Will of Crota, and the second being Crota himself. With the Will of Crota, you get a level 30 -- still manageable, and with a lower spawn rate than the 32 version. Maybe both versions would also spawn Majors; if it happens in a patrol, having someone for others to focus on so that the hunter isn't cut down too quickly would be a good thing. For the 30 version, maybe just acolytes, but for the 32, something a bit more impressive.

The reason why I'm pushing the 30 version is because of the Will of Crota strike is where Eris claims that they'll be coming for you. It also makes sense thematically -- Crota is preparing a foe for you to face for taking out one of his chosen, while the 32 version is punishment being visited upon you by Oryx.

- No text -

I don't think it would be easy to implement in the game, but I DO think it would be a fun plotline in an offline RPG. I would enjoy that in an Elder Scrolls game.

In Destiny, I think there's too much interaction to weaken someone like that...but maybe it would be cool for the other stuff, or if it only happened once.

Or a fan fic. My god that would be fantastic.