Relic

protected override Task InitializeSubscriptions() {
    TrackSubscription(Events.Burst.SubscribeLate(OnBurstLate));
    return Task.CompletedTask;
}

The base class calls InitializeSubscriptions automatically:

• At BeforeCombatStartLate — for relics already in inventory at combat start.
• At AfterObtained when CombatManager.Instance.IsInProgress — for relics obtained mid-combat.

Subscriptions are disposed automatically at AfterCombatEnd and AfterRemoved.

Do NOT call TrackSubscription in BeforeCombatStart

BeforeCombatStart fires before InitializeSubscriptions, and there is no guard preventing double-initialization there. Use BeforeCombatStart only for resetting non-subscription state (e.g. counters):

public override Task BeforeCombatStart() {
    _counter = 0; // reset combat-local state
    return Task.CompletedTask;
}

Persisting State Across Saves — [SavedProperty]

Relic fields that must survive save/load (e.g. cross-combat counters, accumulated values) must be exposed as properties decorated with [SavedProperty].

using MegaCrit.Sts2.Core.Saves.Runs;

private int _accumulatedOverflow;

[SavedProperty]
public int AccumulatedOverflow {
    get => _accumulatedOverflow;
    set {
        AssertMutable();
        _accumulatedOverflow = value;
        InvokeDisplayAmountChanged(); // if used in ShowCounter
    }
}

Rules:

• Must be a property (not a field) with a set accessor.
• Call AssertMutable() at the top of every setter.
• Use SerializationCondition.SaveIfNotTypeDefault to skip saving the default value and keep save data compact.
• When the property drives DisplayAmount, call InvokeDisplayAmountChanged() in the setter.
• private properties are supported (the serializer uses reflection).

When to NOT use [SavedProperty]

• Combat-local counters that should reset every combat — reset in BeforeCombatStart, no attribute needed.
• Derived/computed values — derive them from saved properties instead.
• CancellationTokenSource or other transient runtime objects — never save these.

ShowCounter / DisplayAmount

Override both to surface a counter badge on the relic icon:

public override bool ShowCounter => true;
public override int DisplayAmount => AccumulatedOverflow;

If DisplayAmount is driven by a [SavedProperty], call InvokeDisplayAmountChanged() in the setter so the UI updates live.

AfterObtained Overrides

When overriding AfterObtained for pickup effects (e.g. CapLiberator), always call await base.AfterObtained() last. The base implementation handles mid-combat subscription initialization.

public override async Task AfterObtained() {
    // your pickup logic here
    await base.AfterObtained(); // important: triggers InitializeSubscriptions if in combat
}