Too easy
"Mana steal…" He muttered.
Suddenly, the mana left in the body of the beast started rushing into Harry's hand.
The body itself slowly became pale and pale, until it was no more than bones with patches of meat around it.
[+3200EXP]
Harry nodded his head when he saw the notification that flashed across his eyes.
As expected, mana still did its work as efficiently as usual.
Mana flowed in the bodies of those who could weird it, whether actively or passively. So removing the beast core from a mana beast, doesn't mean its body would suddenly become void of mana.
The mana around its body would still remain there and it was this "residual mana" that Harry absorbed using [Mana steal].
While the EXP was small—as expected, it was still something.
Even though Harry hardly used it so as to avoid the strong mana sense of the instructors, he acknowledged [Mana steal] as a powerful ability.