He answers questions as readily as he asks them, but his answer is always "no."

Sphinx of the Final Word

This spell can't be countered.
Flying
Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Instant and sorcery spells you control can't be countered.

Foundations

Oath of the Gatewatch

Sphinx of the Final Word can't be countered.
Flying, hexproof
Instant and sorcery spells you control can't be countered by spells or abilities.

Oath of the Gatewatch Promos

A spell or ability that counters spells can still target Sphinx of the Final Word or any other spell that can't be countered. When that spell or ability resolves, the spell won't be countered, but any additional effects of the countering spell or ability will still happen.