diff --git a/Seraphina.Tests/Seraphina.Tests.csproj b/Seraphina.Tests/Seraphina.Tests.csproj
index a2352e4..626d8c7 100644
--- a/Seraphina.Tests/Seraphina.Tests.csproj
+++ b/Seraphina.Tests/Seraphina.Tests.csproj
@@ -7,10 +7,15 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="FsCheck.Xunit" Version="2.14.2" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.2.0" />
     <PackageReference Include="xunit" Version="2.4.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
     <PackageReference Include="coverlet.collector" Version="1.0.1" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\Seraphina\Seraphina.csproj" />
+  </ItemGroup>
+
 </Project>
diff --git a/Seraphina.Tests/SkillInfoTest.cs b/Seraphina.Tests/SkillInfoTest.cs
new file mode 100644
index 0000000..eff25fd
--- /dev/null
+++ b/Seraphina.Tests/SkillInfoTest.cs
@@ -0,0 +1,70 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using FsCheck;
+using FsCheck.Xunit;
+using Seraphina.Core;
+using Xunit;
+
+namespace Seraphina.Tests
+{
+    public class SkillInfoTest
+    {
+        static readonly List<SkillPoint> validList = new List<SkillPoint> { 1, 2, 3, 4 };
+
+        [Fact]
+        public void Ctor_ThrowsOnNullAndEmptyId()
+        {
+            Assert.Throws<ArgumentNullException>("id", () => new SkillInfo(null, "test", validList));
+            Assert.Throws<ArgumentException>("id", () => new SkillInfo("", "test", validList));
+        }
+
+        [Fact]
+        public void Ctor_ThrowsOnNullAndEmptyName()
+        {
+            Assert.Throws<ArgumentNullException>("name", () => new SkillInfo("test", null, validList));
+            Assert.Throws<ArgumentException>("name", () => new SkillInfo("test", "", validList));
+        }
+
+        [Fact]
+        public void Ctor_ThrowsOnNullAndEmptySkillCosts()
+        {
+            Assert.Throws<ArgumentNullException>("skillPointCosts", () => new SkillInfo("test", "test", null));
+            Assert.Throws<ArgumentException>("skillPointCosts", () => new SkillInfo("test", "test", new List<SkillPoint> { }));
+        }
+
+
+        [Fact]
+        public void Ctor_ThrowsOnNullDescription()
+        {
+            Assert.Throws<ArgumentNullException>("description", () => new SkillInfo("test", "test", null, validList));
+        }
+
+        public static IEnumerable<object[]> GetSkillInvalidLengths()
+        {
+            for (int i = 1; i < SkillInfo.NumLevelUpgrades; i++)
+            {
+                yield return new object[] { i };
+            }
+        }
+
+
+        [Theory]
+        [MemberData(nameof(GetSkillInvalidLengths))]
+        public void Ctor_ThrowsWhenSkillCostsTooShort(int length)
+        {
+            var skillCosts = Enumerable.Range(0, length).Select(x => new SkillPoint(x)).ToList();
+            Assert.Throws<ArgumentException>("skillPointCosts", () => new SkillInfo("test", "test", skillCosts));
+        }
+
+        [Fact]
+        public void Ctor_AcceptsNormalParameters()
+        {
+            var _ = new SkillInfo("test", "test", validList);
+            // Shouldn't do anything special here, just pass.
+        }
+
+
+
+    }
+}
diff --git a/Seraphina.Tests/SkillManagerTest.cs b/Seraphina.Tests/SkillManagerTest.cs
new file mode 100644
index 0000000..adc7b95
--- /dev/null
+++ b/Seraphina.Tests/SkillManagerTest.cs
@@ -0,0 +1,28 @@
+using Seraphina.Core;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Xunit;
+
+namespace Seraphina.Tests
+{
+    public class SkillManagerTest
+    {
+        private static readonly IEnumerable<SkillPoint> validSkillPointCosts = new[] { 1, 2, 3, 4 }.Select(x => new SkillPoint(x));
+        private static SkillInfo MakeSkill(int id) => new SkillInfo($"id_{id}", $"name_{id}", validSkillPointCosts);
+
+        [Fact]
+        public void Ctor_AddsEventToSkillRepo()
+        {
+            var repo = new SkillRepo();
+            var mgr = new SkillManager(repo);
+
+            var skill = MakeSkill(1);
+
+            repo.AddSkill(skill);
+            Assert.Contains(skill.Id, mgr.Levels.Keys);
+        }
+
+    }
+}
diff --git a/Seraphina.Tests/SkillRepoTest.cs b/Seraphina.Tests/SkillRepoTest.cs
new file mode 100644
index 0000000..5517179
--- /dev/null
+++ b/Seraphina.Tests/SkillRepoTest.cs
@@ -0,0 +1,139 @@
+using FsCheck;
+using FsCheck.Xunit;
+using Seraphina.Core;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Xunit;
+
+namespace Seraphina.Tests
+{
+    public class SkillRepoTest
+    {
+        [Fact]
+        public void Ctor_CanAcceptNoParams()
+        {
+            var repo = new SkillRepo();
+            Assert.Empty(repo.Skills);
+        }
+
+        [Fact]
+        public void Ctor_CanAcceptEmptyEnumerable()
+        {
+            var repo = new SkillRepo(Enumerable.Empty<SkillInfo>());
+            Assert.Empty(repo.Skills);
+        }
+
+        private static readonly IEnumerable<SkillPoint> validSkillPointCosts = new[] { 1, 2, 3, 4 }.Select(x => new SkillPoint(x));
+        private static SkillInfo MakeSkill(int id) => new SkillInfo($"id_{id}", $"name_{id}", validSkillPointCosts);
+
+        private static readonly List<SkillInfo> validSkills = new List<SkillInfo>
+        {
+            MakeSkill(1),
+            MakeSkill(2),
+            MakeSkill(3)
+        };
+
+        [Fact]
+        public void Ctor_SavesSkills()
+        {
+            var repo = new SkillRepo(validSkills);
+
+            Assert.Equal(3, repo.Skills.Count);
+        }
+
+        [Fact]
+        public void Ctor_OverwritesSkillsWithSameId()
+        {
+            var skills = new List<SkillInfo>
+            {
+                new SkillInfo("id1", "name1", validSkillPointCosts),
+                new SkillInfo("id2", "name2", validSkillPointCosts),
+                new SkillInfo("id1", "name3", validSkillPointCosts),
+            };
+
+            var repo = new SkillRepo(skills);
+
+            Assert.Equal(2, repo.Skills.Count);
+            Assert.Equal("name3", repo["id1"].Name);
+        }
+
+        [Fact]
+        public void AddSkill_ThrowsExceptionIfSkillAlreadyExists()
+        {
+            // NOTE: May want to remove this later, depending on future needs.
+            // For instance, overwriting, or skipping.
+            var repo = new SkillRepo(validSkills);
+
+            Assert.Throws<InvalidOperationException>(() => repo.AddSkill(MakeSkill(1)));
+        }
+
+        [Fact]
+        public void AddSkill_AddsSkillToRepo()
+        {
+            var repo = new SkillRepo();
+
+            repo.AddSkill(MakeSkill(1));
+
+            Assert.Single(repo.Skills);
+
+            repo.AddSkill(MakeSkill(2));
+
+            Assert.Equal(2, repo.Skills.Count);
+        }
+
+        [Fact]
+        public void AddSkill_TriggersSkillAddedEvent()
+        {
+            var repo = new SkillRepo();
+
+            var counter = 0;
+            repo.SkillAdded += (sender, e) => counter++;
+
+            repo.AddSkill(MakeSkill(1));
+
+            Assert.Equal(1, counter);
+
+            repo.AddSkill(MakeSkill(2));
+
+            Assert.Equal(2, counter);
+        }
+
+        [Fact]
+        public void AddSkill_DoesNotTriggerSkillAddedEventIfInvalidParameter()
+        {
+            var repo = new SkillRepo();
+
+            var counter = 0;
+            repo.SkillAdded += (sender, e) => counter++;
+
+            repo.AddSkill(MakeSkill(1));
+
+            Assert.Equal(1, counter);
+
+            try
+            {
+                repo.AddSkill(MakeSkill(1));
+            }
+            catch (InvalidOperationException) { }
+
+            Assert.Equal(1, counter);
+        }
+
+        [Fact]
+        public void SkillAdded_GivesAddedSkill()
+        {
+            var repo = new SkillRepo();
+
+            var skill = MakeSkill(1);
+
+            var str = "";
+            repo.SkillAdded += (obj, e) => str = e;
+
+            repo.AddSkill(skill);
+
+            Assert.Equal(skill.Id, str);
+
+        }
+    }
+}
diff --git a/Seraphina.Tests/UnitTest1.cs b/Seraphina.Tests/UnitTest1.cs
deleted file mode 100644
index 09aab11..0000000
--- a/Seraphina.Tests/UnitTest1.cs
+++ /dev/null
@@ -1,14 +0,0 @@
-using System;
-using Xunit;
-
-namespace Seraphina.Tests
-{
-    public class UnitTest1
-    {
-        [Fact]
-        public void Test1()
-        {
-
-        }
-    }
-}
diff --git a/Seraphina/Seraphina.csproj b/Seraphina/Seraphina.csproj
index c73e0d1..74fe973 100644
--- a/Seraphina/Seraphina.csproj
+++ b/Seraphina/Seraphina.csproj
@@ -3,6 +3,11 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp3.1</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="System.Collections.Concurrent" Version="4.3.0" />
+  </ItemGroup>
+
 </Project>
diff --git a/Seraphina/SkillInfo.cs b/Seraphina/SkillInfo.cs
new file mode 100644
index 0000000..13f2b22
--- /dev/null
+++ b/Seraphina/SkillInfo.cs
@@ -0,0 +1,76 @@
+#nullable enable
+
+using Seraphina.Core;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Seraphina
+{
+    /// <summary>
+    /// Contains information about a skill.
+    /// </summary>
+    public class SkillInfo
+    {
+        public static readonly int NumLevelUpgrades = Enum.GetValues(typeof(SkillLevel)).Length - 1;
+
+        public string Id { get; }
+        public string Name { get; }
+        public string Description { get; }
+        public IReadOnlyList<SkillPoint> UpgradeCost { get; }
+
+        public SkillInfo(string id, string name, IEnumerable<SkillPoint> skillPointCosts)
+            : this(id, name, "", skillPointCosts) { }
+
+        public SkillInfo(string id, string name, string description, IEnumerable<SkillPoint> skillPointCosts)
+        {
+            if (id is null) throw new ArgumentNullException(nameof(id));
+            if (id.Length == 0) throw new ArgumentException("Must not be empty", nameof(id));
+            if (name is null) throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0) throw new ArgumentException("Must not be empty", nameof(name));
+            if (description is null) throw new ArgumentNullException(nameof(description));
+
+            if (skillPointCosts is null) throw new ArgumentNullException(nameof(skillPointCosts));
+
+            var lst = skillPointCosts.ToList();
+            if (lst.Count() < NumLevelUpgrades)
+                throw new ArgumentException($"Must have at least {NumLevelUpgrades} entries", nameof(skillPointCosts));
+
+            Id = id;
+            Name = name;
+            Description = description;
+
+            UpgradeCost = lst;
+        }
+
+        /// <summary>
+        /// Gets the <see cref="SkillPoint"/> cost required to upgrade the skill from the
+        /// current level.
+        /// </summary>
+        /// <param name="currentLevel">The skill's current level.</param>
+        /// <returns>
+        /// A <see cref="SkillPoint"/> value, or null if the skill is at max level.
+        /// </returns>
+        public SkillPoint? CostToUpgrade(SkillLevel currentLevel)
+        {
+            if (currentLevel == SkillLevel.Master) return null;
+
+            return UpgradeCost[(int)currentLevel];
+        }
+
+        public SkillPoint CostToMaster(SkillLevel currentLevel = SkillLevel.Untrained)
+        {
+            var level = (int)currentLevel;
+
+            SkillPoint sum = 0;
+
+            for (int i = level; i < (int) SkillLevel.Master; i++)
+            {
+                sum += UpgradeCost[i];
+            }
+
+            return sum;
+        }
+    }
+}
diff --git a/Seraphina/SkillLevel.cs b/Seraphina/SkillLevel.cs
new file mode 100644
index 0000000..7584dc2
--- /dev/null
+++ b/Seraphina/SkillLevel.cs
@@ -0,0 +1,11 @@
+namespace Seraphina
+{
+    public enum SkillLevel
+    {
+        Untrained,
+        Trained,
+        Skilled,
+        Advanced,
+        Master
+    }
+}
diff --git a/Seraphina/SkillManager.cs b/Seraphina/SkillManager.cs
new file mode 100644
index 0000000..29a7115
--- /dev/null
+++ b/Seraphina/SkillManager.cs
@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace Seraphina
+{
+    /// <summary>
+    /// Manages the skill list for a player, keeping track of their levels.
+    /// </summary>
+    public class SkillManager : IDisposable
+    {
+        private readonly SkillRepo Repo;
+        public Dictionary<string, SkillLevel> Levels { get; } = new Dictionary<string, SkillLevel>();
+
+        public event EventHandler<(SkillInfo, SkillLevel)>? SkillUpgraded;
+
+        public SkillManager(SkillRepo repo)
+        {
+            Repo = repo;
+            Repo.SkillAdded += Repo_OnSkillAdded;
+
+            foreach (var item in repo.Skills.Keys)
+            {
+                Levels[item] = SkillLevel.Untrained;
+            }
+        }
+
+        private void Repo_OnSkillAdded(object? sender, string e) => Levels[e] = SkillLevel.Untrained;
+
+        #region IDisposable Support
+        private bool disposedValue = false; // To detect redundant calls
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposedValue) return;
+
+            if (disposing)
+            {
+                Repo.SkillAdded -= Repo_OnSkillAdded;
+            }
+
+            disposedValue = true;
+
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+        #endregion
+
+    }
+}
diff --git a/Seraphina/SkillRepo.cs b/Seraphina/SkillRepo.cs
new file mode 100644
index 0000000..81e260c
--- /dev/null
+++ b/Seraphina/SkillRepo.cs
@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Seraphina
+{
+    /// <summary>
+    /// Contains a list of all the in-game skills.
+    /// </summary>
+    public class SkillRepo
+    {
+        public ConcurrentDictionary<string, SkillInfo> Skills { get; } = new ConcurrentDictionary<string, SkillInfo>();
+
+        public event EventHandler<string>? SkillAdded;
+
+        public SkillRepo() : this(Enumerable.Empty<SkillInfo>()) { }
+        public SkillRepo(IEnumerable<SkillInfo> skills)
+        {
+            // TODO: Should skills with duplicate IDs be checked?
+            foreach (var skill in skills)
+            {
+                Skills[skill.Id] = skill;
+            }
+        }
+
+        public SkillRepo AddSkill(SkillInfo skill)
+        {
+            string id = skill.Id;
+            if (Skills.ContainsKey(id)) throw new InvalidOperationException($"Skill {skill.Id} already exists.");
+
+            Skills[id] = skill;
+
+            OnSkillAdded(id);
+
+            return this;
+        }
+
+        protected void OnSkillAdded(string skillId) => SkillAdded?.Invoke(this, skillId);
+
+        public SkillInfo this[string idx] => Skills[idx];
+    }
+}