My friend who hasn't played since 7th edition is looking to get back into the game, what are the biggest rules changes since then that she should be aware of?
Ok, let’s see… I’m going to take this chronologically so that I don’t miss anything. I won’t talk about new set mechanics, but I will try to mention any major mechanics that became evergreen.
Mirrodin block introduced equipment, which are printed in almost every set these days.
Kamigawa block introduced the vigilance keyword and the first major change to the legend rule in many years. The legend rule was changed again a few more times before it settled into its current iteration where the legend rule only applies to each player individually. New copies of legendary permanents can be cast, but only one can be kept at a time.
Ravnica block introduced hybrid mana.
Time Spiral block introduced a ton of new keyword abilities, many of which would go on to become evergreen, such as flash, lifelink, deathtouch, shroud, etc.
Lorwyn introduced the Planeswalker card type with all of its associated rules. Planeswalker rules would be modified for Ixalan to make them legendary and Dominaria will get rid of planeswalker redirection as a concept.
Magic 2010 brought with it the largest rules change since Sixth Edition. The major changed it brought were as follows:
Terminology changes: The “in-play” zone became the battlefield, the “removed from the game” zone became the exile zone and “remove from the game” as an action became exile, spells started to be cast rather than played again and activated abilities started to be activated rather than played, the “end-of-turn step” became the end step and “at end of turn” triggers became “at the beginning of the end step” triggers.
Mana pool changes: Mana burn was removed as a concept, and the mana pool emptied as each step and phase ended rather than at the end of each phase.
Combat damage changes: Combat damage no longer uses the stack. Instead, combat damage is dealt immediately after it’s assigned. To still allow for counterplay with regards to this, combat damage can no longer be assigned freely among the creatures blocking or blocked by a creature. Instead, there is now a damage assignment order chosen for those creatures when blockers are declared and the first creature in the order must be assigned lethal damage before any damage can be assigned to the next creature in line, etc.
Deathtouch and lifelink became static abilities that modify the effects of damage rather than triggered abilities.
Innistrad block introduced double-faced cards and checklist cards to represent them in decks.
Oath of the Gatewatch introduced the new colorless mana symbol, as well as some cards with a specific colorless cost.
Kaladesh block introduced vehicles and the energy mechanic.
Those are all of the big changes that I can think of off the top of my head. I think your friend should be fine if they read up on these things and go from there.
