If your life total is brought to 0 or less at the same time that creatures you control are dealt lethal damage, you lose the game before the last ability goes on the stack.

In a Two-Headed Giant game, Bastion of Remembrance's last ability causes the opposing team to lose 2 life and you to gain 1 life.

If one or more creatures you control die at the same time that Bastion of Remembrance leaves the battlefield, its last ability triggers for each of those creatures.