Below is a basic Rising World Unity plugin example that lets a player throw fireballs which can damage NPCs and destroy terrain blocks.
This assumes the Rising World Unity Java plugin API (same structure as other RW plugins).

It works like this:

Player types /fireball

A fireball projectile spawns in front of the player

It flies forward

On impact it:

destroys terrain blocks in a small radius

damages nearby NPCs

Rising World Unity Fireball Plugin
package fireballplugin;

import net.risingworld.api.Plugin;
import net.risingworld.api.Server;
import net.risingworld.api.World;
import net.risingworld.api.Player;
import net.risingworld.api.objects.Npc;
import net.risingworld.api.utils.Vector3f;
import net.risingworld.api.Timer;

import java.util.List;

public class FireballPlugin extends Plugin {

    @Override
    public void onEnable() {
        System.out.println("Fireball Plugin Loaded");
    }

    @Override
    public void onPlayerCommand(Player player, String command, String[] args) {

        if (command.equalsIgnoreCase("fireball")) {

            Vector3f pos = player.getPosition();
            Vector3f dir = player.getViewDirection();

            spawnFireball(player, pos, dir);
        }
    }

    public void spawnFireball(Player player, Vector3f pos, Vector3f dir) {

        final Vector3f fireballPos = new Vector3f(
                pos.x + dir.x * 2,
                pos.y + 1.5f,
                pos.z + dir.z * 2
        );

        final Vector3f velocity = new Vector3f(
                dir.x * 0.6f,
                dir.y * 0.6f,
                dir.z * 0.6f
        );

        Timer timer = new Timer(50, true, () -> {

            fireballPos.x += velocity.x;
            fireballPos.y += velocity.y;
            fireballPos.z += velocity.z;

            checkImpact(player, fireballPos);

        });

        timer.start();
    }

    private void checkImpact(Player player, Vector3f pos) {

        World world = getServer().getWorld();

        int x = Math.round(pos.x);
        int y = Math.round(pos.y);
        int z = Math.round(pos.z);

        int block = world.getBlock(x, y, z);

        if (block != 0) {

            explode(player, pos);
        }
    }

    private void explode(Player player, Vector3f pos) {

        World world = getServer().getWorld();

        int radius = 3;

        for (int x = -radius; x <= radius; x++) {
            for (int y = -radius; y <= radius; y++) {
                for (int z = -radius; z <= radius; z++) {

                    world.setBlock(
                            (int)pos.x + x,
                            (int)pos.y + y,
                            (int)pos.z + z,
                            0
                    );

                }
            }
        }

        List<Npc> npcs = world.getNpcs();

        for (Npc npc : npcs) {

            if (npc.getPosition().distance(pos) < 5) {

                npc.damage(50);

            }
        }

        player.sendTextMessage("Fireball exploded!");
    }
}
plugin.yml
name: FireballPlugin
version: 1.0
main: fireballplugin.FireballPlugin
author: YourName
How to Install

Create a plugin folder:

/plugins/FireballPlugin/

Compile the Java file

Put the compiled .jar inside the plugin folder

Restart the server

In-game type:

/fireball
What This Plugin Currently Does

✔ Player can cast fireballs
✔ Fireball travels forward
✔ Breaks terrain blocks
✔ Damages NPCs
✔ Explosion radius