Found this error in the logs and though I would report it here.

Logs:
[22:27:48.048] [.NET ThreadPool Worker/WARN] [tML]: Silently Caught Exception:
System.Exception: The localization key:
"Mods.BossChecklist.LogMessage.MustContainName"
with a value of:
"Invalid internal name passed ({internalName}). Your call must contain a string comprised of letters and/or digits without whitespace characters in order to generate an entry key."
failed to be formatted with the inputs:
[Ultros(2nd)]
at Terraria.Localization.LocalizedText.Format(Object[] args) in tModLoader\Terraria\Localization\LocalizedText.TML.cs:line 97
at BossChecklist.BossChecklist.LogWarning(String key, Boolean requiresConfig, Object[] args) in BossChecklist.cs:line 93
at BossChecklist.BossChecklist.Call(Object[] args) in BossChecklist.cs:line 180
at FF6Mod.FF6World.DoBossChecklistIntegration() in FF6Mod\FF6World.cs:line 600
at FF6Mod.FF6World.PostSetupContent() in FF6Mod\FF6World.cs:line 318
at Terraria.ModLoader.SystemLoader.PostSetupContent(Mod mod) in tModLoader\Terraria\ModLoader\SystemLoader.cs:line 65
at Terraria.ModLoader.ModContent.<>c.<Load>b__43_2(Mod mod) in tModLoader\Terraria\ModLoader\ModContent.cs:line 315
at Terraria.ModLoader.ModContent.LoadModContent(CancellationToken token, Action`1 loadAction) in tModLoader\Terraria\ModLoader\ModContent.cs:line 377
at Terraria.ModLoader.ModContent.Load(CancellationToken token) in tModLoader\Terraria\ModLoader\ModContent.cs:line 313
at Terraria.ModLoader.ModLoader.Load(CancellationToken token) in tModLoader\Terraria\ModLoader\ModLoader.cs:line 127
at Terraria.ModLoader.ModLoader.<>c__DisplayClass47_0.<BeginLoad>b__0() in tModLoader\Terraria\ModLoader\ModLoader.cs:line 107
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.<>c.<.cctor>b__272_0(Object obj)
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
at System.Threading.Thread.StartCallback()

[22:27:48.050] [.NET ThreadPool Worker/ERROR] [BossChecklist]: Call Error: at Terraria.Localization.LocalizedText.Format(Object[] args) in tModLoader\Terraria\Localization\LocalizedText.TML.cs:line 104
at BossChecklist.BossChecklist.LogWarning(String key, Boolean requiresConfig, Object[] args) in BossChecklist.cs:line 93
at BossChecklist.BossChecklist.Call(Object[] args) in BossChecklist.cs:line 180 The localization key:
"Mods.BossChecklist.LogMessage.MustContainName"
with a value of:
"Invalid internal name passed ({internalName}). Your call must contain a string comprised of letters and/or digits without whitespace characters in order to generate an entry key."
failed to be formatted with the inputs:
[Ultros(2nd)]
[22:27:48.050] [.NET ThreadPool Worker/INFO] [ColoredDamageTypes]: [ColoredDamageTypes] Cross-mod type already exists, changing default colors provided by mod. FF6Mod.Items.BlitzDamage.BlitzDamageClass
[22:27:48.050] [.NET ThreadPool Worker/INFO] [ColoredDamageTypes]: [ColoredDamageTypes] Cross-mod type already exists, changing default colors provided by mod. FF6Mod.Items.Tools.ToolsDamageClass