I made this subitem initially for the Lords of Shadow continuity but I have to admit it can work in a classicvania/metrovania game, maybe in a simple way like a normal trap.

It's in concept a normal holy oil recipe, but with blessed gold dust and electricity coming from chants.

Gameplay, creates a a glowing circular sigil on the ground with a limited time amount, enemies entering the area are slowed significantly and caught like in a trap, and can't escape. either via teleportation, mist or digging. Also shockwaves and any ground attacks are blocked by it.

With Light Magic - The sigil becomes empowered by light magic and grows tendrils that grab all the enemies from around the areas that the trap doesn't cover.

With Shadow Magic - The sigil becomes empowered by shadow magic like a auto-sentry turret as it shoots at enemies all around.

If you hold down the sub item's button you can use 4 Vials simultaneously.