From UO Resurgence WIKI

Halloween is celebrated every year for the entire month of October and ends after the first five days in November. 2020 is the first year of the shard's re-birth and therefore is the first year of celebrating the Halloween event.

Pumpkins have started growing in farmer's fields. These pumpkins come in two varieties, pumpkins that can be carved and pumpkins that cannot be carved. The carved pumpkins can only be carved with special pumpkin carving kits. Both types of pumpkins will grow to random sizes. Additionally, there is some hocus pocus at work in the pumpkin fields! There have been reports of Jack O Lantern's in the fields! When these Jack O Lantern's are moved a killer pumpkin will appear to stop the one who moved it! This killer pumpkin has something supernatural about it! try using Silver weapons against it! Killer pumpkins have a rare chance to drop one of five hand painted masks as loot. Be Careful! These jack O Lantern's come with three different names!

Trick Or Treat
Walking up to any vendor in any city and saying trick or treat will result in you receiving some special Halloween candy or a trick being done on you. Additionally, if you have GM begging you will have a chance at receiving a rare Halloween gift as a treat! These rare Halloween gifts are as follows:
a Creepy Cake
a Pumpkin Pizza
a Grim Warning
Harvest Wine
Murky Milk
Mr. Plain's Cookies
Skulls On a Pike
Chair In A Ghost Costume
Excellent IronMaiden
Halloween Guillotine
Colored Small Webs

The Butcher
The Butcher is a demon that has invaded cemeteries across the land. He can be found in the Firebriar, Eaglevale, or Freylyn Cemeteries. Additionally, the Butcher can be found in the remains of an old city near Tallenbrook. The Butcher has a chance to drop a pumpkin carving kit as loot.

Zombie Skeletons
Anytime you die during the Halloween event, your character will have a chance spawn as a zombie skeleton somewhere in a cemetery. This zombie skeleton will have a chance to drop a bones container that will have your character's name on it.