Scragnoth

• WOTC Official Reminder Textofficial rules
  Protection — This permanent can't be damaged, enchanted, equipped, blocked, or targeted by [quality].

• WWizards of the Coast2004-10-04
  Official Ruling
  Spells with a side effect that only happens if a spell is countered do not have their side effect happen when the countering fails.
• WWizards of the Coast2004-10-04
  Official Ruling
  Side-effects of spells that would counter this card will still happen, because they happen even if the spell they’re trying to counter can’t be countered.
• WWizards of the Coast2004-10-04
  Official Ruling
  Spells can target Scragnoth and affect it while it is on the stack. Only effects that counter spells are ignored.

Rulings via Scryfall