Fixes#1690. Addresses Blood Oath holistically — three bugs found while researching the spell against RunUO, ServUO, the UODemise/uo.com guides, and the archived UOGuide page.
## Bugs fixed
### 1. Expiry timing (the filed issue)
The `ExpireTimer` polled every 1s, so expiry and death/delete cleanup lagged up to ~1s. Replaced with a **single-shot** timer plus centralized `[OnEvent]` handlers on `PlayerDeathEvent`/`PlayerDeletedEvent`/`CreatureDeathEvent`/`CreatureDeletedEvent` — the oath now breaks immediately on death/delete of either party.
### 2. Duration formula
Used `/80` (the bugged in-game tooltip value) instead of the real OSI formula `((SpiritSpeak - Resist) / 8) + 8`. Confirmed by RunUO, ServUO, the emulator guides, and the code's own fixed-point comment. At GM Spirit Speak this changes duration from ~9.5s to 23s and makes Spirit Speak actually affect duration.
### 3. Damage reflection (`BaseCreature.Damage` vs `PlayerMobile.Damage`)
`BaseCreature.Damage` diverged: it attributed the reflected hit to the attacker itself (`from.Damage(amount, from)`) instead of the caster, reflected the bonused (not original) amount, used `×1.1` vs `×1.2`, lacked the caster-survival guard, and had no Publish 48 resist mitigation.
Unified both paths: reflect the **original** damage attributed to the **caster** at `×1.2`. Publish 48 resist mitigation now applies only to creature casters and is gated behind `Core.SA`.
## Internals
- Collapsed the parallel `_oathTable` into a single `_table` keyed by both participants → shared timer, so `RemoveCurse` resolves from either side (required by the event handlers).
- Extracted `GetDurationSeconds` and `ComputeReflectedDamage` as testable statics.
## Tests
13 new tests (duration formula, reflection mitigation, oath lifecycle, end-to-end event-driven removal). Full suite: **436/436 pass**.
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