Create-A-Card Competition

BOO!
22
Cast spell
Spells and abilities on the stack are assigned random targets (if applicable).
Speed

Trick or Treat!
111
Cast spell
Equal chance of:
Give opponent a random card - OR -
Steal a random card from opponent
Speed

Magical Costume Shop
222
Create unique building
(Speed Summon)
(Fleeting)
Target monster receives a random costume modifier
Speed

Ghost Costume
Zero
Attach modifier
Monster neither deals nor receives any damage and gains type "ghost"

Witch Costume
Zero
Attach modifier
Monster gains "Target monster takes 15 damage" and type "witch"
Speed

Lame Costume
Zero
Attach modifier
Monster has -15 attack and takes 15 damage and gains (decoying)

[More costume modifiers to come when I feel like it]