When using Carnivine's "Return" attack, do I have to draw until there are five cards in my hand, or may I stop with less than five?
You do not have to draw any cards, but if you choose to do so you must end up with exactly five cards in your hand; no more, no less.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH3_5
SWSH3_5
SM12_89
SM12_89
HGSS4_28
HGSS2_29