When you reduce a creature that isn't a construct or undead to 0 hitpoints, you can choose to cast this spell to make an additional attack against a creature in range. Additionally until the spell ends, your speed is doubled, you gain a +2 bonus to AC, you have advantage on Dexterity saving throws, and gain an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.

After you cast this spell, at the beginning of each your turns, you must make a constitution saving throw of 10 + 1 for each turn this spell is active. If failed take 2d10 necrotic damage and the spell ends prematurely.

When the spell ends, the target can't move or take actions until after its next turn, as a wave of lethargy sweeps over it.

As an action, you can choose to dispel Hollowed Haste without suffering the affects of lethargy.