-Stages outside the castle, seen in CV3, Adventure, and 4.
-Treemen, seen in CV4 and X68000
-Statues crumble causing damage, seen in CV4
-First time Medusa's whole body is present for her boss fight
-First appearance of the Mudmen
-First time we see paintings for background effects, especially with the painting of the woman crying bloody tears
-First appearance of the eyeball enemies from Adventure and BR (Different tho, these ones come from the wall and bounce, no explosions)
-Second boss is the Aquarius boss in CV3
-First series nudity, seen on the topless harpies(usually saved for statues and Medusa later in the series. Maybe not influence, but it is the first time)
-Stained glass boss, returns in X68000 as a mini-boss type enemy, normal enemy in CV64/LoD
-Mummies come out of coffins to attack, seen in COTM
-First appearance on Golem
-Frankenstein hitting wall to make bricks fall, seen in CV3, attacking with chains seen in X68000
-First appearance of a crumbling bridge
-Final stage song is Julius's theme in Aria
Also, some of us wondered about Bloody Tears in HC, same composer as CV2, and I guess he saw the painting while developing the soundtrack and decided to put a mix of his classic Simons Quest song in there so it'd fit.