Teferi's Ultimate Nightmare

This spell can't be countered. (Obviously.)
When you cast this spell, choose one:
• You get an emblem with "Permanent spells you
cast cost {3} less to cast and have Cascade X. (As Cascade, but repeat X times, where X is the number
of untapped Islands your opponents control.)"
• You get an emblem with "Whenever a spell you control is countered by a source an opponent controls, that source's controller loses the game."