Did the requested changes.

src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/magical/MagicPills.java

@@ -1,11 +1,10 @@
 package io.github.thebusybiscuit.slimefun4.implementation.items.magical;
 
+import io.github.thebusybiscuit.cscorelib2.inventory.ItemUtils;
 import org.bukkit.Sound;
 import org.bukkit.entity.EntityType;
-import org.bukkit.entity.Player;
 import org.bukkit.entity.Villager;
 import org.bukkit.entity.ZombieVillager;
-import org.bukkit.inventory.EquipmentSlot;
 import org.bukkit.inventory.ItemStack;
 
 import io.github.thebusybiscuit.slimefun4.api.MinecraftVersion;
@@ -19,7 +18,7 @@ import me.mrCookieSlime.Slimefun.api.SlimefunItemStack;
 
 /**
  * This {@link SlimefunItem} allows you to convert any {@link ZombieVillager} to
- * their {@link Villager} variant.
+ * their {@link Villager} variant. It is also one of the very few utilisations of {@link EntityInteractHandler}.
  *
  * @author Linox
  *
@@ -34,20 +33,13 @@ public class MagicPills extends SimpleSlimefunItem<EntityInteractHandler> {
 
     @Override
     public EntityInteractHandler getItemHandler() {
-        return (e, item) -> {
+        return (p, entity, item, offhand) -> {
-            if (e.getRightClicked().getType() == EntityType.ZOMBIE_VILLAGER) {
+            if (entity.getType() == EntityType.ZOMBIE_VILLAGER) {
-                Player p = e.getPlayer();
-
-                item.setAmount(item.getAmount() - 1);
-                if (e.getHand() == EquipmentSlot.OFF_HAND) {
-                    p.getInventory().setItemInOffHand(item);
-                } else {
-                    p.getInventory().setItemInMainHand(item);
-                }
 
+                ItemUtils.consumeItem(item, false);
                 p.playSound(p.getLocation(), Sound.ENTITY_ZOMBIE_VILLAGER_CONVERTED, 1, 1);
 
-                ZombieVillager zombieVillager = (ZombieVillager) e.getRightClicked();
+                ZombieVillager zombieVillager = (ZombieVillager) entity;
                 zombieVillager.setConversionTime(1);
                 if (SlimefunPlugin.getMinecraftVersion().isAtLeast(MinecraftVersion.MINECRAFT_1_15)) {
                     zombieVillager.setConversionPlayer(p);

src/main/java/me/mrCookieSlime/Slimefun/Objects/handlers/EntityInteractHandler.java

@@ -3,6 +3,7 @@ package me.mrCookieSlime.Slimefun.Objects.handlers;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.Player;
 import org.bukkit.event.player.PlayerInteractAtEntityEvent;
+import org.bukkit.inventory.EquipmentSlot;
 import org.bukkit.inventory.ItemStack;
 
 import me.mrCookieSlime.Slimefun.Objects.SlimefunItem.SimpleSlimefunItem;
@@ -15,6 +16,7 @@ import me.mrCookieSlime.Slimefun.Objects.SlimefunItem.SlimefunItem;
  *
  * @see ItemHandler
  * @see SimpleSlimefunItem
+ * @see PlayerInteractAtEntityEvent
  *
  */
 @FunctionalInterface
@@ -24,10 +26,16 @@ public interface EntityInteractHandler extends ItemHandler {
      * This function is triggered when a {@link Player} right clicks with the assigned {@link SlimefunItem}
      * in his hand.
      *
-     * @param e
+     * @param p
-     *            The {@link PlayerInteractAtEntityEvent} that was triggered
+     *            The {@link Player} that right clicked
+     * @param entity
+     *            The {@link Entity} that was right clicked on
+     * @param item
+     *            The {@link ItemStack} that was held and used while triggering
+     * @param offHand
+     *            <code>true</code> if the {@link EquipmentSlot} is off hand
      */
-    void onInteract(PlayerInteractAtEntityEvent e, ItemStack item);
+    void onInteract(Player p, Entity entity, ItemStack item, boolean offHand);
 
     @Override
     default Class<? extends ItemHandler> getIdentifier() {

src/main/resources/languages/researches_en.yml

@@ -233,3 +233,4 @@ slimefun:
   tree_growth_accelerator: Faster Trees
   industrial_miner: Industrial Mining
   advanced_industrial_miner: Better Mining
+  magic_pills: De-Zombification