Hunger of Hadar - Warlock Attack 5

[Plane Sailing]

PHB page 278, on Durations: <...> Starting on the turn after you create an effect, you sustain the effect by taking the indicated action: a standard action, a move action, or a minor action. (You can sustain an effect once per turn.) <...>

So no, you can't sustain it multiple times per turn, nor can you do it in the same turn you cast it. Nice try, though .

My mistake was in forgetting that sustain has a specific meaning (extend the duration in subsequent rounds) combined with the secondary attack which takes place when you do the sustain.

It's a shame, because I love the idea of spending extra actions to urge 'my pretties' on

Cheers