Cast Shard of the Nightbringer by paying ({5} magic symbol) ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Shard of the Nightbringer triggers, causing an opponent to lose half their life total, rounded up, and you to gain life equal to the life lost this way.
Enduring Tenacity triggers, causing the opponent to lose life equal to the amount of life gained this way.
The opponent loses the game due to having zero or less life.