## Summary
After #2670, `BaseCreature` stores one master. Callers still reached it through three differently gated names plus hand-rolled combinations of the `Controlled`/`Summoned` flags. Each gate is now one named view:
| Member | Definition | Meaning |
|---|---|---|
| `Master` | the reference; its setter does the follower bookkeeping; serialized as before | whoever the creature answers to |
| `ControlMaster` | `Controlled ? Master : null` | the owner |
| `SummonMaster` | `Summoned ? Master : null` | the summoner |
| `GetMaster()` | `ControlMaster ?? SummonMaster` | who answers for the creature |
`ControlMaster` and `SummonMaster` stay settable so custom code keeps compiling: both setters assign `Master`. There is no guard, so a write through either one can read back as null until the matching flag is set.
An enraged creature is the one shape with a master and neither flag. It keeps its meer through `Master`, while `GetMaster()` stays null, so the meer never answers for it (notoriety, kill credit).
Readers move onto the view they mean:
- "Owner or summoner" pairs and `ControlMaster ?? SummonMaster` collapse into `GetMaster()`: pack instinct, familiars, golem, house access, mounts, pack horse, Solen friendship, spell target and guild checks, and the `[` pet command.
- Checks such as `Controlled && ControlMaster == from` drop the flag the view already applies. Checks that don't reduce keep it: `Controlled && ControlMaster != from`, a possibly-null `from`, and `MageAI.CanDispel`'s `Summoned &&`.
**No behavior change, save format unchanged** (the schema generator produces no diff). Edge cases for custom code and shard operators:
- `SummonMaster = x` on a plain pet now replaces its owner (#2670 made that a no-op), and `ControlMaster = null` on an uncontrolled summon now clears its caster (it did nothing before).
- `SpellHelper.GetGuildFor` no longer falls back to an enraged creature's meer. Meer mages have no guild.
## Docs
- `dev-docs/content-patterns.md` § Masters: which view answers which question, how to set a master, and which flag checks are redundant.
- `dev-docs/runuo-migration-docs/09-items-mobiles-creatures.md` § Masters: RunUO's two-field reads mapped onto the views, plus the gotcha for creatures that set `SummonMaster` without `Summoned` (the write compiles, the read now returns null; use `Master`).
- The `modernuo-content-patterns` and `migrate-items-mobiles` skills point at both.
## Test plan
- [x] `MasterViewsTests`: all four views across wild, pet, controlled summon, uncontrolled summon and enraged shapes; reassigning `Master` moves follower slots; `SetControlMaster(null)` keeps an uncontrolled summon's caster; deleting a summon returns the caster's slots
- [x] Serialization tests updated to the new views (round-trip, legacy v22, v23 migration)
- [x] UOContent.Tests (1178 passed, 2 skipped) and Server.Tests (907) green
## Summary
`BaseCreature` stored the pet owner (`ControlMaster`) and the summoner (`SummonMaster`) in two fields. Every flow that manages pets kept them in step by hand: summon, transfer, stable, claim, ball of summoning and GM obey. They now share one `_master` field, and the two properties read it through the Controlled and Summoned flags:
```csharp
ControlMaster => Controlled ? master : null
SummonMaster => Controlled && !Summoned ? null : master
```
Every existing reader keeps its meaning:
- `ControlMaster` is still "the owner".
- `SummonMaster` is still "the summoner, controlled or not".
Blade spirits, energy vortexes, clones, undead minions and enraged creatures (a summon master without `Summoned`) never become visible through `ControlMaster`, so the ungated readers (ML notoriety, aggressor entries and similar) behave as before.
- Setting `SummonMaster` on a plain pet does nothing, instead of quietly replacing the owner.
- `SetControlMaster` now keeps both masters in step, so the hand-written `SummonMaster` copies are removed from ball of summoning, GM obey, pet transfer, auto-stable and claim, the animal trainer's stable and claim, and jail stabling.
## Serialization
BaseCreature moves to v24 with one serialized master (slot 15); the old `SummonMaster` slot is dropped.
- `MigrateFrom(V23Content)` resolves absent fields through the same default-value methods the live reader uses.
- A save that carried both masters (a summon traded before ownership followed transfers) resolves to the owner. Legacy pre-codegen streams follow the same rule.
Requires `ModernUO.Serialization.Generator` 4.2.0 (#2671). `UOContent.Tests` was still on 4.1.0 and is bumped to match.
## Test plan
- [x] `MasterShapes_RoundTrip`: controlled pet, controlled summon, energy vortex, enraged creature
- [x] `SummonMaster_OnPlainPet_KeepsTheOwner`: owner and follower counts unchanged
- [x] `LegacyV22Stream_DifferingMasters_OwnerWins`
- [x] `V23Stream_MigratesToOneMaster_AndDefaultsAbsentFields`: both master slots -> owner; flags past bit 32; absent fields take class defaults
- [x] UOContent.Tests (1168 passed, 2 skipped) and Server.Tests (907) green
The pure SerializationGenerator conversion of `BaseCreature`, split out of #2592 so it can serve as the reference for converting every other large hand-written class in the Delta Saves project (#7, phase 3). Two behaviour changes from #2592 are deliberately not here and follow in their own PRs on top of this one: `SpeedClass`, and the collapse of `ControlMaster`/`SummonMaster` into one reference (a creature can lose or keep either independently: Blade Spirits and Energy Vortexes are summoned but never controlled, EnragedCreature and talisman summons keep a summon master with neither flag set).
## What this is
- `BaseCreature` becomes `[SerializationGenerator(23, false)]` with a `[SerializableField]` per serialized slot and `[SaveFlag]` elision on nearly every field, so a stock creature serializes to its version plus flags. Field orders run 0..53 with no gaps (54 fields).
- The hand-written reader stays as `private void Deserialize(IGenericReader reader, int version)` for every pre-codegen version (0..22); post-codegen bumps use `MigrateFrom` from here on. `[AfterDeserialization]` carries the post-load fixups main did after reading (stat timers, AI type, followers, reacquire seeding).
- `ControlMaster` and `SummonMaster` stay two independent fields with main's semantics, each elided when null.
- `DamageMin`/`DamageMax`/`ActiveSpeed`/`PassiveSpeed` are no longer virtual (nothing in the tree overrode them); comments swept to the constraints that matter.
- Direct writes to serialized backing fields outside the generated setters (`SetDamage`, `SetResistance`, the move-speed helpers, the loot flag, feed loyalty, the delete timer) call `this.MarkDirty()`, matching the #2609 standard, so the class is ready for delta saves once `Mobile` is audited.
- Schema `Server.Mobiles.BaseCreature.v23.json` regenerated by the tool (a second run produces no diff).
## Deferred to follow-up PRs
SpeedClass: the serialized `_speedClass` field, `DefaultSpeedClass` replacing the type constant, `ApplySpeedClass`/`OnSpeedClassChange`, "None means custom", the four-speeds-as-one-block elision, `NPCSpeeds.FindEntry(SpeedLevel)`, the constructor fallback to Medium, and their tests.
Master references: serializing one `Master` with a `Controlled`/`Summoned` fan-out and the `SetControlMaster` lockstep.
## Tests
UOContent.Tests 776 / Server.Tests 855 green. `BaseCreatureSerializationTests` covers: a default creature elides to version + flags; a populated creature round-trips with exact byte consumption; back-to-back saves are byte-identical; an uncontrolled summon keeps its SummonMaster; byte-authentic v22 legacy streams (replicas of main's `Serialize`) load through the legacy reader for a wild tamable, a controlled pet, a controlled summon with an anchored `SummonEnd`, and a summon-master-only creature (the EnragedCreature shape); a running delete timer round-trips through `[DeserializeTimer]`; `Friends`, `CurrentWayPoint` and `HomeMap` round-trip; a `BaseVendor` stub round-trips the generated BaseVendor v2 → generated BaseCreature v23 chain.
## Behaviour notes for reviewers
- `ActiveMoveSpeed`/`PassiveMoveSpeed` getters return the raw override (0 = inherit); `CurrentMoveSpeed` is the resolved pace.
- Speeds elided as table defaults re-snap to the current `npc-speeds.json` on load, so table edits reach unmodified spawns on restart.
- `GetSpeeds` no longer throws on the save/load path when the table has no entry for the type: saves elide against the creature's own values and loads keep the stream. Construction still throws (`InvalidOperationException`, was `KeyNotFoundException`). An elided load with no table entry would otherwise resume at speed 0, so `[AfterDeserialization]` logs once and paces it at Medium.
- `virtual` removed from `ActiveSpeed`, `PassiveSpeed`, `DamageMin`, `DamageMax` (no overrides in the tree; forks may have some).
- `ControlMaster`, `SummonMaster`, `ControlOrder`, `Tamable`, `IsParagon` are `[SerializableProperty]` over hand-written setters because follower bookkeeping must run before the assignment, which a `fieldChanged` hook cannot express; the wire format is identical.
## Prerequisites for cherry-picking
#2609 (BaseVendor is already generated on top of BaseCreature) and SerializationGenerator 4.1.0.
Kamron Batman