2019-01-25 : A creature spell that can't be countered is a legal target for Essence Capture. The spell won't be countered when Essence Capture resolves, but you'll still put a +1/+1 counter on the target creature.

2019-01-25 : You can't cast Essence Capture without a target creature spell. If either target is illegal when Essence Capture tries to resolve, the other is still affected as appropriate.