Whenever another creature dies, put a +1/+1 counter on Elenda, the Dusk Rose.
When Elenda dies, create X 1/1 white Vampire creature tokens with lifelink, where X is Elenda's power.
1/19/2018 If Elenda dies at the same time as another creature, both of its triggered abilities trigger. However, the first one won’t do anything since you can’t put a +1/+1 counter on Elenda.
1/19/2018 To determine how many Vampire tokens are created, use Elenda’s power as it last existed on the battlefield.
1/19/2018 If Elenda would die and it’s your commander in the Commander variant, you may put it into the command zone instead. However, if you save Elenda this way, it doesn’t die and you won’t create any Vampire tokens.