Hi all,
The update is still pretty new and there's a bit on confusion about what all the items are and how they can be used so I'm trying to collate all of the information we know so far about the halloween 2012 update. I haven't added any of the wave 666 yet because I haven't had time to try it!


IMPORTANT What I have written below is merely from my own observation and is not complete please help by replying with screenshots or observations of your own which I can add to the post.



Gift drop spawns

You will get a notification when a present spawns. Only you will be able to see/collect the present, it will remain on the map for a set amount of time. Another notification will show if the gift disappears before you find it. Gifts seem to contain different spells (detailed below) or cursed items (I think I got 6 all in the same gift).

An in-depth look at the gift dropping mechanics are given in a post by Cyphafrost, many thanks dude.

Current known locations:

Known spawn point for halloween gifts, click for full size

Marasmus

Huntsman possibly deals bonus damage (full charged headshot reads as 1080 damage) bodyshots seem to deal 3x base damage

Players heads sometimes turn into bombs. If this happens to you the game view will switch to 3rd person mode. Touching Merasmus as a bomb will stun him, also granting you crits and uber for a short time. While Merasmus is stunned he takes crit damage and he cannot attack.

Mersamus can teleport around the map.

If he teleports to the mid point he will start an animation where he lifts the bombinomicon above his head, flies up and drops bombs all around mid point. During this team he appears to have an enormous hitbox and take crit damage.

At ~ half health Mersasmus goes and "hides" as a prop on the map. His health bar turns green to indicate he is hiding. When a prop is damaged it gives off green goop until it explodes and ejects a crit boost pumpkin.

Currently known props and locations can be seen in this album: http://imgur.com/a/31X35#0

Note that the props are are within the "middle" region of the map and along the battlements. While most of the props are very obvious some of them include rocks, a large pumpkin, a grandfather clock, and a coffin - all of which can spawn near the medium ammo pack at the end of the battlements closest to the pool room slightly out of the way.

Killing Merasmus

Preparation: Merasmus is difficult to kill, not because he is strong or good at killing players, but because he only appears on the map for around 3 mins at a time. Therefore it is extremely important for all players on the map to focus Merasmus, doing this will kill him easily. A good tactic appears to be for all players to go huntsman sniper except one engineer. Engineers build dispensers and teleporters in the pool room, don't need to bother with sentries - they tend to be more hassle than it's worth.

Attacking strategy: Both teams should not kill each other nor capture the point. Merasmus will spawn after a few minutes and all players should aim for fully charged headshots. TWO players at a time will turn into bombs that can stun Merasmus. It is a good tactic for one player to stun Merasmus, the other waits until the stun has almost worn off before stunning him again. When Merasmus hides as a prop in the map as discussed above everyone should split up and destroy the props. It is important that this is done as quickly as possible or he will leave before you can kill him. Two or three hits with a kukri will kill each prop, and engineers can use shotguns and pistols to help out.

When Merasmus flies above the point dropping bombs the best tactic is to stand away from the point and shoot him from long range. Anyone near the point will be killed by the bombs. Standing in the pool room is mostly sheltered, the dispensers there can be beneficial to resupply the health and ammo of players attacking merasmus. Wrangled sentries don't seem to be particularly effective against him. He takes crit damage during this time so a charged bodyshot from the huntsman will deal 1080 damage. Basically just fling arrows in his general direction.

He then usually goes and hides as a prop a second time when he's nearly dead. You know what to do.

After the second prop hunt he'll teleport back into the map and you just have to finish him off. He often targets just one person and chases them down. If he starts chasing you try and lead him back to the middle of the map so both teams can attack him easily.

Skull island

When Merasmus is killed he completes a death animation then leaves a floating bombomnicon for a few seconds in the place that he died. touching this teleports the player to skull island. Same setup as with monoculous, not much there, get achievement and hat by passing into the skull and touching the bombomnicon. This teleports the player back into the map with crit, speed and uber boost.

Staying on the island for more than ~20 seconds results in the island exploding, killing on players still there.


Series #51 Eerie Crate

Drops randomly as a crate or can sometimes be found in "pile of curses." When opened with an eerie key the crate may drop one of the following (I think it can also drop potions in conjunction with an item listed below):

Anything above without any information on its restriction is probably not restricted, but is not confirmed yet!


Pile of curses

Crafting together 7 cursed items creates a "pile of curses" which appears in the back pack (Crafting > fabricate special > fabricate pile of curses -or- use custom blueprint). Using the pile of curses ("reaching in") is like opening a crate, except free: you will randomly receive an item with either "unique" or "haunted" quality. A "voodoo-cursed soul" is a misc item which can be equipped by the corresponding class, turning your character into a zombie.

There is also a small chance of finding an Eerie crate (crate series #51) in conjunction with a "soul" misc. As far as we know "Haunted" and "Unique" look identical in game (just like "vintage" vs. unique).


Spells

Spells can be found in gifts on the map, also sometimes found in eerie crates in conjunction with the misc/hat in the crate and in "pile of curses" in conjunction with a "voodoo-cursed soul". Known spells so far:

Voice effect spells:

If you add a voice changer to an all class hat it will change the voice of all classes not just the one it was meant for (Thanks Epicake)

Particle effect spells: "Footstep" effect spells:
Add these to hats, any class wearing a hat with a spell on it will have a crazy awesome trail of footprints. Paint effect spells:
Add these to hats, any class wearing a hat with a spell on it will have a crazy awesome trail of footprints.

Using a paint

All spells expire on Nov 8th/9th (at the end of the tf2 halloween period)


Edit: Thank you so much to everyone who has contributed to this thread. I've tried to give credit, although some people both submitted the same content so apologies if I missed you, your contribution is still appreciated! <3

Thanks also to imgur for the image hosting, the reddit community for their contributions and support, and the tf2 wiki for additional support and information along with steam forums.

Peace,
Camilo