Well been as its the silly season, ond one of the teams I work with decided to put their decorations up 2 weeks ago, I told them the naughty elf was coming to get them as they had killed some elves…
Day 1 - office chairs hidden and all jacket sleeves had knots tied in them…
So what’s your suggestions to torture these naughty ladies 
Tomorrow - they’ve left a big tub of salt out so… Piles of salt on their chairs
Fake cat poop in the salt
Level 1 Evil:Saran wrap computer monitors
Level 2: Saran Wrap toilet seats
Changing keyboard settings?
Unplugging mice?
Changing screen savers to an elf ?
Changing wallpapers to an elf ?
Whiteboard marker on windows
Brussel sprouts in their drawer?
FLOUR on their desk and the elf doing a snow angel in it…
For workspace tampering, I’m going to be really boring and say please don’t mess with their settings or chair heights. I have set settings on mine for my back and even just disconnecting my headset messes with my sound settings when I plug it back in. This stresses me out when systems don’t work like they’re supposed to!
But setting the screen to go upside down or moving the mouse to the otherside of the keyboard, things like that are elf annoying but won’t affect people too badly. You don’t want to upset people.
Even just leave a ‘threatening’ elf message to say something has heen done & actually do nothing with get people waiting in anticipation for it all day 
Now THAT is evil.
Thanks folks, got quite a few bits planned, especially cling filming you chairs, monitors, taping up things keep them coming…
@JoCat anyone with back problems won’t be harmed… All fun but no torture
If you can get a couple of the key caps off the keyboard without breaking them and swap them round some fun could be had. 
Hide the kettle!
Unfortunately it’s a boiler mounted to the wall
Lol I’d put whoopee cushions in their chairs and use the salt to replace the sugar in the staff room and then do little elf footprints all over their desks! 
Mark toilet doors as out of order !
I thought they were quite tame
Yuuup
If they’re not technical, switch their monitor screen upside down - ‘Ctrl+Alt+{down arrow}’ Or left/right arrow. Unless know the keyboard shortcut, very disorientating to get into settings to flip it back.
Unfortunately might need to when they leave PC unlocked and unguarded
Ahhh there must be a stop cock to stop it refilling