My first attempt at implementing a card.

Mage.Sets/src/mage/cards/b/BurntOffering.java

@@ -0,0 +1,149 @@
+/*
+ *  Copyright 2010 BetaSteward_at_googlemail.com. All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without modification, are
+ *  permitted provided that the following conditions are met:
+ *
+ *     1. Redistributions of source code must retain the above copyright notice, this list of
+ *        conditions and the following disclaimer.
+ *
+ *     2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *        of conditions and the following disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY BetaSteward_at_googlemail.com ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ *  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BetaSteward_at_googlemail.com OR
+ *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ *  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ *  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ *  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *  The views and conclusions contained in the software and documentation are those of the
+ *  authors and should not be interpreted as representing official policies, either expressed
+ *  or implied, of BetaSteward_at_googlemail.com.
+ */
+package mage.cards.b;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+import java.util.UUID;
+
+import mage.Mana;
+import mage.abilities.Ability;
+import mage.abilities.costs.Cost;
+import mage.abilities.costs.common.SacrificeTargetCost;
+import mage.abilities.effects.Effect;
+import mage.abilities.effects.OneShotEffect;
+import mage.cards.CardImpl;
+import mage.cards.CardSetInfo;
+import mage.choices.Choice;
+import mage.choices.ChoiceImpl;
+import mage.constants.CardType;
+import mage.constants.Outcome;
+import mage.game.Game;
+import mage.game.permanent.Permanent;
+import mage.players.Player;
+import mage.target.common.TargetControlledCreaturePermanent;
+
+/**
+ *
+ * @author Topher
+ */
+public class BurntOffering extends CardImpl {
+    
+    public BurntOffering(UUID ownerID, CardSetInfo setInfo) {
+        super(ownerID, setInfo, new CardType[]{CardType.INSTANT},"{B}");
+        
+        //As an additional cost to cast Burnt Offering, sacrifice a creature.
+        this.getSpellAbility().addCost(new SacrificeTargetCost(new TargetControlledCreaturePermanent()));
+        //Add to your mana pool an amount of {B} and/or {R} equal to the sacrificed creature's converted mana cost.
+        this.getSpellAbility().addEffect(new BurntOfferingEffect());
+    }
+    
+    public BurntOffering(final BurntOffering card) {
+        super(card);
+    }
+    
+    @Override
+    public BurntOffering copy() {
+        return new BurntOffering(this);
+    }
+}
+
+class BurntOfferingEffect extends OneShotEffect {
+        
+    public BurntOfferingEffect() {
+        super(Outcome.PutManaInPool);
+        this.staticText = "Add X mana in any combination of {R} and/or {B} to your mana pool,"
+                + " where X is the sacrificed creature's casting cost";
+    }
+    
+    public BurntOfferingEffect(final BurntOfferingEffect effect) {
+        super(effect);
+    }
+    
+    @Override
+    public boolean apply(Game game, Ability source) {
+        Player player = game.getPlayer(source.getControllerId());
+        if (player != null) {
+            Choice manaChoice = new ChoiceImpl();
+            Set<String> choices = new LinkedHashSet<>();
+            choices.add("Red");
+            choices.add("Black");
+            manaChoice.setChoices(choices);
+            manaChoice.setMessage("Select color of mana to add");
+            
+            int xValue = getCost(source);
+            
+            for(int i = 0; i < xValue; i++) {
+                Mana mana = new Mana();
+                while(!player.choose(Outcome.Benefit, manaChoice, game)) {
+                    if(!player.canRespond()) {
+                        return false;
+                    }
+                }
+                if(manaChoice.getChoice() == null) {  //Can happen if player leaves game
+                    return false;
+                }
+                switch(manaChoice.getChoice()) {
+                    case "Red":
+                        mana.increaseRed();
+                        break;
+                    case "Black":
+                        mana.increaseBlack();
+                        break;
+                }
+                player.getManaPool().addMana(mana, game, source);
+            }
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public Effect copy() {
+        return new BurntOfferingEffect(this);
+    }
+    
+    /**
+     * Helper method to determine the CMC of the sacrificed creature.
+     * @param sourceAbility
+     * @return 
+     */
+    private int getCost(Ability sourceAbility) {
+        for(Cost cost : sourceAbility.getCosts()) {
+            if(cost instanceof SacrificeTargetCost) {
+                SacrificeTargetCost sacrificeCost = (SacrificeTargetCost) cost;
+                int totalCMC = 0;
+                for(Permanent permanent : sacrificeCost.getPermanents()) {
+                    totalCMC += permanent.getConvertedManaCost();
+                }
+                return totalCMC;
+            }
+        }
+        return 0;
+    }
+}

Mage.Sets/src/mage/sets/IceAge.java

@@ -74,6 +74,7 @@ public class IceAge extends ExpansionSet {
         cards.add(new SetCardInfo("Blue Scarab", 233, Rarity.UNCOMMON, mage.cards.b.BlueScarab.class));
         cards.add(new SetCardInfo("Brainstorm", 61, Rarity.COMMON, mage.cards.b.Brainstorm.class));
         cards.add(new SetCardInfo("Brushland", 327, Rarity.RARE, mage.cards.b.Brushland.class));
+        cards.add(new SetCardInfo("Burnt Offering", 4, Rarity.COMMON, mage.cards.b.BurntOffering.class));
         cards.add(new SetCardInfo("Caribou Range", 235, Rarity.RARE, mage.cards.c.CaribouRange.class));
         cards.add(new SetCardInfo("Celestial Sword", 289, Rarity.RARE, mage.cards.c.CelestialSword.class));
         cards.add(new SetCardInfo("Centaur Archer", 360, Rarity.UNCOMMON, mage.cards.c.CentaurArcher.class));