These items have spells on them.

What are spells?
Spells were a tool item, that are no longer available. They use to be distributed during TF2's Halloween event, but haven't since the 2014 event.
Spells would give items various Halloween themed effects for during full moon/Halloween event.
The only way to get spell effects now is to trade for items that already have spells applied to them.
Items with spells have became popular among item collectors.

What are they worth?
These are collectible items so the value can be subjective.
Spells use to be tradable prior to the Tough Break Update (December 2015). Spells first didn't dropping during the 2015 Halloween event (October 2015), during that 2 month period when Spells were still tradable the value and desire of spells jumped up significantly. Particularly, Footprint Spells were selling as high as 20-50 Keys.
There are numerous items with spells on the market today with various listed prices. Factors that could be contributed to value are what exact spell, the item it is applied, the combination/synergy, etc.

What Do These Spells Look Like?
Footprint Spells causes flames being left in the player's wake as they run.
Footprint Spells were like the rare 'unusual' drops of Spells.
Headless Horseshoes Footprints are Purple.
Bruised Purple Footprints are Red.
Rotten Orange Footprints are Orange.
Corpse Gray Footprints are Green

Paint Spells for cosmetic items, causes the item to shift between different colors.
Putrescent Pigmentation - slow fade lighter and darker shades of yellowish-green
Spectral Spectrum - fast fade team color to either; while on RED team yellow/orange/red, or while on BLU team to white.
Sinister Staining - fast fade lighter and darker shades of yellowish-green

Check out this Youtube video (by Strife) to see what the spells effects look like: https://www...kDXW0E
There is more info on spells on the tf2 wiki: https://wiki.teamfortress.com/wiki/Halloween_Spells

1. Beep Man (W/ Footprint Spell: Bruised Purple Footprints + Paint Spell: Putrescent Pigmentation) for 40 Keys
2. S.H. Ghost of Spies Checked Past (W/ Halloween Spell: Corpse Gray Footprints) for 30 Keys
4. V. TM's Tossle Cap (W/ Footprint Spell: Rotten Orange) for 30 Keys
3. Bruiser's Bandanna (W/ Footprint Spell: Headless Horseshoes) for 30 Keys
5. S. Villain's Veil (W/ Paint Spell: Sinister Staining) for 10 Keys
6. S.H. Tiny Texan (W/ Paint Spell: Putrescent Pigmentation) for 10 Keys
7. The Bruiser's Bandanna (W/ Spectral Spectrum) for 10 Keys
More I have for trade: http://www.tf2outpost.com/trade/29502283

Considering offers. Mainly looking for pure.
Please leave offers in the comments below.
Send A Trade Offer Or Add Me If Interested.
Trade Offer Link: https://steamcommunity.com/tradeoffer/new/?partner=12087337&token=OSsqIT6F

Can sell through marketplace.tf (Not currently listed on the site).
Not interested in paypal / steam market.
Hey man, could you do 7 keys for the veil? i can easily get the pure
lmao footprints don't add 30 keys
6 keys for bandana spectral
This trade is done, so you can't post. Sorry, mate.