UPDATES - Downvoters please comment. I can't help you if you don't let me.
- Added to level 9 guide.
- Iron Skull required now it may be easier to do co-op. This guide was from a single player perspective. Can always use save and quit exploit.
- Apparently if you were in co-op and didn't get the achievement, viewing the playlist unlocks it. (Tokisaki Jr)
- Some changes for conciseness.
I don't really record videos or anything so I can't give a step by step guide, but figured I could put some general tips until someone makes a 'real guide'. Also things that may have messed me up.
1. If a fight is skippable, skip it. This generally only works if its a level involving vehicles in some way, but there were a few moments in the first level where I just rushed past everyone while I had overshield.
2. Punching is your friend. Unless I had a power weapon, the best way to fight an Elite one on one was a punch fight. Be warned though punching can be annoying and can take a bit to get used to since you don't have the magic commando punch from the other Halo games.
3. Graphics. I would generally go to the old graphics because it makes it more obvious when you're actually hitting an Elite (shield shimmer), plus the newer graphics don't line up with the level geometry.
I generally only used higher graphics on Flood-Based levels.
4. Grenades. With the Boom skull on, you need to be VERY careful with explosives. Frequently, throwing a grenade will blow up just about everything in the entire room. Also, even with the increased blast radius, they don't do more damage. So they're best to use against mobs of Grunts, Jackals, or Flood. (Or chance one after you've killed the little guys to try to blow up the whole room.)
5. Hunters. You can beat them in melee fights. Their melee has 2 damaging periods, the upswing and the downswing. If you don't get hit by the down swing you should be good. I'm not sure if it does more damage than the upswing but I tended to die more often from it, possibly from collision with objects or the level geometry.
The upswing will only take out about 3/4 of your shield.
Assault Rifle - I generally only found it nice for the ammo. Use if you have nothing else.
Pistol - Good against Flood, Grunts, Jackals, and Hunters.
Sniper Rifle - Good against everything except flood. DO NOT USE AGAINST FLOOD.
Shotgun - Must have once its available (level 6). Kills most enemies in 3 or less hits.
Rocket Launcher - I generally wouldn't advise using one if you see it, especially with double ammo usage.
Frags - BE CAREFUL WHEN USING. SEE ABOVE.
7. Vehicles. Honestly, all the vehicles in this game are pretty bad. The aiming reticule for most of them don't line up with where you actually shoot. I only use the tank during Assault on the Control Room for the big chasm room. Any other times I had vehicles were generally just to skip things.
General Level Tips -
1. When you have overshields, try to skip fights. I skipped the fight during the room with the winding staircase, and punched my way through the covenant that kill the unarmed guys later in the level. Also be careful near the end when you get grenades, you can easily blow up the entire room and kill yourself. Try to get Elites to come to you so you can get used to the necessary fist fighting the black eye skull forces on you.
2. I advise using the Warthog, so you'll have to fight at the first area. Generally I'd let the Elites come to me and beat them in a punch fight. In the bridge room, slam your Warthog into the wall and run up the slant to the bridge button, then get back to your Warthog and drive out of the cave. During the marine defense, I would generally spend most of the time running down people with the Warthog, getting out only to punch people or get a health pack.
The sniper rifle is a good choice for the group that is entrenched in the buildings.
Extra Tips from Fozzeyyy
- After you have your Warthog, you only have to fight at one of the 3 groups of marines for evac, so you let the other 2 die and then actually fight at the third one.
Other Misc Tips
- You CAN grenade jump over the gap, but it can be dangerous with the double blast radius. Plus, this leaves you with low shields for the next room. Try at your own risk.
3. Sniper Rifle. When you reach the ridge where she says to go on the left to sneak around them. Do that. If you keep hugging the wall you eventually reach an active camo. Use this to rush to the elevator and beat down everyone. There are dead marines with a whole bunch of grenades that are good for taking out the elevator enemies.
Inside is a bit tricky, I would grab the invisibility right away and kill all the sword Elites. After you get through the tunnels I would suggest jumping down in the big room where you're supposed to open the door for the marines (they're probably all dead at this point) and then go through one of the doors under the walkway you just jumped down from. You can't open the doors yourself until the enemies are dead, but you can run past the enemies that come through them. You may have to kill some of the enemies in the room to cause these reinforcements to come in.
The only other tips I could give specific to this level is to grab the invisibility in the first brig to kill the guys where Keyes is. Be VERY careful when escorting Keyes, I've had him kill me with the needler.
Extra Tips from Fozzeyyy
- Kill the invisible Elite and then run through the door you'd normally go through after dispatching the enemies (once they've opened it for you). Once music starts playing, go back for the camo and kill everyone in the room.
4. The beach charge can be hit or miss based off how crazy people go with their grenades. When you have the Warthog, skip the first area (where the door would normally slam shut on you) and go straight to the second area. Try to run over the herd of Jackals around the trees. No real specific tips about the next area, just make good use of the overshields.
When you go back to the area you skipped, drive the Warthog inside, this will make it easier to get out later.
Once inside the area you skipped, as you enter the room with the Elite in front of you, assassinate him and move through the door on the right. Hug the right wall until you reach a hole in the floor. Head left after you drop down to the health packs, then start jumping down the cliffs to the lower levels, first to the left, then straight down and down the ramp. Look over the edge to see an overshield next to a box. Try to jump on this (or skim the edge of the box it's next to). Then just run inside and hit the switch.
Turn around and leave the way you came in, going up the ramp. Take out the Elite and all the Grunts and work your way out (going left and up the ramp after killing the Elite). There will be Jackals coming down the curved ramp which can be pretty annoying to take out (or at least they were for me). In the room after this ramp, go right and through the door on your right and there will be an active camo. Using this you should be able to make it all the way back up to the health packs. If there are enough supplies left here you can probably grenade spam your way to the next ramp. You'll want to fight the enemies in the last room while hiding down here, at least initially.
The sword Elite at the door can be annoying - I only had my assault rifle left. I led him out of the room and for some reason he froze in place so I just kept pelting him. Drive the Warthog out and off the building. When the pelican arrives, go back up and jump in.
Extra Tips from Fozzeyyy
- You can ignore the beach fight if you want. Just turn around and start heading for the area where you open the door to the map room.
5. Long level so I can't remember too much, but a few things.
- Use your grenades on the first Elites so they don't mess you up too bad.
- Rush through any area with sleeping Grunts, I believe there are 2 or 3 of these areas.
- Be careful in the tank because its blast radius is so big and its reticule is so terrible. Only fight with it when you're in the big room with the bridge.
- When you exit this room, grab a ghost and rush to the all the way to the cave past the spiral hill (where you meet the marines retreating from Hunters). There will be a camo right before it (behind a rock on the left). Grab it and rush to the building.
- When you get to the parallel bridges, jump on the glass wall to jump to the other bridge. Head in the door on the same wall you came out of.
- There is camo in the hallway with all the camo Elites. Use it to rush past the next enemies and to a banshee. Fly this banshee to the control room.
- Grenade the hell out of the guys inside the big door.
6. Really easy level honestly, the pistol does very well against the flood. Just melee to keep your shields up. This level shouldn't be a problem if you've gotten this far. Against a lone flood you can easily melee your shield up. Even infection forms work.
7. Move VERY slowly. Fight every single group and focus on trying to keep a pistol and shotgun. Careful with grenades. There are 2 or 3 spots that at least to me seemed to infinitely spawn enemies (they would jump off the big blue fish tank things) so you may need to rush past enemies at some points. If you have any time where you feel like the enemies just keep coming, I'd suggest dying and just trying to rush past it so you have the ammo. Just melee people as you push through.
8. The beginning is really horrible. Try to spam the grenades to weaken the sentinels, then just work on shotgunning them while popping out from the glass walls. In the next room, if you're lucky, most of the enemies will kill each other, which is honestly the only way I can see to do it. When I made it everyone had died except 2 Jackals, which ran around the corner so they weren't shooting me the whole time. Use your shotgun on Elites. Go up top the spiral ramp for a pistol.
Slide down the left side of the pyramid until you get to the last path for a rocket launcher. Use this for the Elites and the Wraith. The pistol is good for finishing the wraith if its the last enemy.
After you do the first shield drain thing, be careful as sentinels come in through the door. Try to melee one on your way out.
When you get to the double bridge - DO NOT SKIP IT LIKE LAST TIME.
There are several flood spawning triggers that seem to have to happen in order to trigger checkpoints, so just fight through everyone.
Be careful in the long hallway as there is a rocket flood, although there are Elites in the hallway so they may kill him.
When you get to the long cave, I'd advise trying to skip everything with a Banshee, although there are roughly 5 rocket flood that can be annoying to dodge.
9. There is an active camo on the left through the first door (where the armless flood is following the Grunt from). This will get you past the inside enemies, as well as the first outside group.
During the outside part, try to run past things as many areas have infinite flood. At the elevator, for me everyone just blew up for some reason, so try grenades.
When leaving Keyes' room, walk to the exit so the Fuel Rod Grunts see you. Then go back and hide in the corner. This will cause the Flood and Covenant to fight.
When escaping, jump down the floors to steal the banshee.
10. Skip the cutscene in the bridge so the Sentinels don't break the windows.
Grab a Rocket Launcher and Shotgun from the armory down the hall from the engine room when you get there. I'd advise grabbing the guns and getting out fast so you don't have to fight all the invisible flood.
I'd also advise using the right path to get to the top and staying up there the whole time since after you break some engines the flood constantly spawn outside the doors on the way up.
Break 2 engines then try to find somewhere to hide for a checkpoint, if you do have to go down, go up the right path again as its easier.
I broke the 2 engines on the right side of the room, then went towards the elevator you use after breaking all 4. When I turned back towards the room I got a checkpoint.
For the Warthog part, just be careful to stay away from enemies as you pretty much have to do it in one go. Feel free to get out and punch things if you have to.
At the end, move out to the right to make your way along the path.