Champion of the Weird's ability by paying 1 life and putting two -1/-1 counters on it.
If
Champion of the Weird does not die as a state-based action due to having 0 or less toughness, resolve the ability from step 1, causing an opponent to blight 2, and continue activating the ability until
Champion of the Weird dies.
When
Champion of the Weird dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
When
Champion of the Weird enters,
Trostani triggers, causing you to gain 7 life.
Resolve the
Champion of the Weird ability from step 1, causing an opponent to blight 2.