They add mana to your mana pool and do not use the stack
Shadow Lugia was only released as a promotion for Pokmon XD: Gale of Darkness for the GameCube
If you're playing casually, theres nothing stopping you from adding them to your deck, but if youre considering following a tournament format, you should check which cards are banned
(That creature returns under its owner's control.) Whenever this creature attacks, you may exile target creature defending player controls until this creature leaves the battlefield
Sword of Hearth and Home can also be used to untap a creature that you attacked with, letting one of your creatures play at having vigilance
Final Fantasy IIs Firion, Wild Rose Warrior, gives equipped creatures haste (meaning they can attack immediately) and creates short-lived copies of your equipment when you play it