If instead the creature you control is an illegal target but the creature you don't control is still a legal target, nothing will happen when Rabid Gnaw resolves
Newer titles have moved away from the paradigm of the heroes of light collecting the scattered crystals in favor of broader, more convoluted plot-lines, but most games in the series still have a crystalline element somewhere
However, they will disappear once the final chapter ability resolves
Counterspells in general can feel pretty bad for the player affected, and theres a political tension in how much bullying you can get away with
Unlike many other cEDH commanders, it isnt locked into a single win condition, so you have multiple paths to close games depending on the situation
Olivia effectively turns your graveyard into a second hand, making board wipes much less effective against you