Rpg Maker Developers Group

Hi everyone!
I'm trying to make my first game on RPG Maker MV and I'm encountering a problem, I have no idea what to do.

Basically, for my game, my character will have a skill that allows him to throw a fireball, except this is not done in battle, but in the map. This fireball can be used to melt ice crystals that are blocking the way, for example. For now, I have created an event called "fireball", which has no image, and when the player uses the skills, it moves the event on them, changes its appearance to a fireball, moves a few cases in the direction the player is facing, and then goes back to having no appearance. I also have a common event that checks if the fireball is on the same tile as the crystal, in which case they both disappear.

The thing I'm having trouble with is when to adjusting passability. If I put both the fireball and the crystal on the same level as the player, the fireball just stops and disappears before hitting the crystal. I don't know if I can change that about the crystal, since I want it to block the player's path. If I put the fireball as a passable ("through" in the options box), it starts going through walls and other objects, which I don't want it to do. I tried using Yanfly's Region Restriction plugin, but it's not working for me, since I want the tile to block the player when the ice crystal is there, but to let the player pass when the ice crystal is melted. I also tried using the RED_SetRegionID plug in to change the region ID after the crystal is gone, but my character is still unable to go through.

So basically, my question is, is there a way to make an event passable for other events, but not for the player?

Thank you!