Add Mentor mechanic

src/magic/model/MagicAbility.java

@@ -649,6 +649,12 @@ public enum MagicAbility {
             }
         }
     },
+    Mentor("mentor", 0) {
+        @Override
+        protected void addAbilityImpl(final MagicAbilityStore card, final Matcher arg) {
+            card.add(ThisAttacksTrigger.Mentor);
+        }
+    },
 
     // abilities that involve SN
     ShockLand("As SN enters the battlefield, you may " + ARG.COST + "\\. If you don't, SN enters the battlefield tapped\\.", -10) {

src/magic/model/target/MagicTargetFilterFactory.java

@@ -2281,6 +2281,16 @@ public class MagicTargetFilterFactory {
         }
     };
 
+    public static final MagicPermanentFilterImpl MENTOR = new MagicPermanentFilterImpl() {
+        @Override
+        public boolean accept(final MagicSource source, final MagicPlayer player, final MagicPermanent target) {
+            final MagicPermanent mentor = (MagicPermanent)source;
+            return target.isCreature() &&
+                target.isAttacking() &&
+                target.getPower() < mentor.getPower();
+        }
+    };
+
     /**
      * Single texts completely specifying the targeting condition.
      */

src/magic/model/trigger/ThisAttacksTrigger.java

@@ -1,12 +1,16 @@
 package magic.model.trigger;
 
+import magic.model.MagicCounterType;
 import magic.model.MagicGame;
 import magic.model.MagicPermanent;
 import magic.model.event.MagicEvent;
 import magic.model.event.MagicSourceEvent;
 import magic.model.event.MagicExertEvent;
 import magic.model.choice.MagicMayChoice;
+import magic.model.choice.MagicTargetChoice;
 import magic.model.action.EnqueueTriggerAction;
+import magic.model.action.ChangeCountersAction;
+import magic.model.target.MagicTargetFilterFactory;
 
 public abstract class ThisAttacksTrigger extends AttacksTrigger {
     public ThisAttacksTrigger(final int priority) {
@@ -51,4 +55,26 @@ public abstract class ThisAttacksTrigger extends AttacksTrigger {
             }
         };
     }
+
+    public static ThisAttacksTrigger Mentor = new ThisAttacksTrigger() {
+        @Override
+        public MagicEvent executeTrigger(final MagicGame game, final MagicPermanent permanent, final MagicPermanent attacker) {
+            return new MagicEvent(
+                permanent,
+                new MagicTargetChoice(
+                    MagicTargetFilterFactory.MENTOR,
+                    "an attacking creature you control with lesser power than " + permanent
+                ),
+                this,
+                "PN puts a +1/+1 counter on target attacking creature with less power than SN.$"
+            );
+        }
+        @Override
+        public void executeEvent(final MagicGame game, final MagicEvent event) {
+            event.processTargetPermanent(game, permanent -> {
+                game.doAction(new ChangeCountersAction(event.getPlayer(), permanent, MagicCounterType.PlusOne, 1));
+            });
+        }
+    };
+
 }