diff --git a/server/escalation.py b/server/escalation.py
new file mode 100644
index 0000000..1e81f05
--- /dev/null
+++ b/server/escalation.py
@@ -0,0 +1,121 @@
+"""Escalation engine — intensity curve, phase params, stochastic timing."""
+
+import math
+import random
+import time
+
+from server.config import config
+
+
+class EscalationEngine:
+    """Computes intensity and rendering parameters from elapsed time.
+
+    Intensity follows a logarithmic curve: intensity = log(1 + elapsed * rate).
+    Rendering parameters are derived from intensity and clamped to [0, 1].
+    Timing intervals are randomized within ranges that shrink with intensity.
+    """
+
+    PALETTES = [
+        "void_black", "crimson_void", "deep_rot", "sickly_green",
+        "bruise_purple", "ash_grey", "bile_yellow", "blood_orange",
+    ]
+
+    def __init__(self, rate: float | None = None):
+        self.rate = rate if rate is not None else config.escalation.rate
+        self.session_start: float | None = None
+
+    def start_session(self) -> None:
+        """Begin a new escalation session."""
+        self.session_start = time.monotonic()
+
+    def reset(self) -> None:
+        """Restart the session from zero."""
+        self.session_start = time.monotonic()
+
+    def get_elapsed(self) -> float:
+        """Seconds since session start."""
+        if self.session_start is None:
+            return 0.0
+        return time.monotonic() - self.session_start
+
+    def get_intensity(self, elapsed: float | None = None) -> float:
+        """Compute intensity from elapsed seconds. Logarithmic, never peaks."""
+        if elapsed is None:
+            elapsed = self.get_elapsed()
+        return math.log(1 + elapsed * self.rate)
+
+    def get_phase_params(self, intensity: float | None = None) -> dict:
+        """Derive rendering parameters from current intensity.
+
+        All values clamped to [0, 1]. Higher intensity = more severe effects.
+        """
+        if intensity is None:
+            intensity = self.get_intensity()
+
+        def _sigmoid(x: float, midpoint: float = 2.0, steepness: float = 1.5) -> float:
+            """Smooth 0→1 mapping centered at midpoint."""
+            return 1.0 / (1.0 + math.exp(-steepness * (x - midpoint)))
+
+        morph_speed = _sigmoid(intensity, midpoint=1.5, steepness=1.2)
+        shader_severity = _sigmoid(intensity, midpoint=2.0, steepness=1.0)
+        voice_frequency = _sigmoid(intensity, midpoint=2.5, steepness=0.8)
+        noise_level = _sigmoid(intensity, midpoint=3.0, steepness=1.0)
+        surprise_chance = min(1.0, _sigmoid(intensity, midpoint=3.5, steepness=0.6))
+
+        # Palette shifts to more aggressive colors at higher intensity
+        palette_index = min(int(intensity), len(self.PALETTES) - 1)
+
+        return {
+            "morph_speed": round(morph_speed, 3),
+            "shader_severity": round(shader_severity, 3),
+            "voice_frequency": round(voice_frequency, 3),
+            "noise_level": round(noise_level, 3),
+            "surprise_chance": round(surprise_chance, 3),
+            "palette": self.PALETTES[palette_index],
+        }
+
+    def get_asset_swap_interval(self, intensity: float | None = None) -> float:
+        """Random interval until next asset swap. Shrinks with intensity."""
+        if intensity is None:
+            intensity = self.get_intensity()
+        cfg = config.escalation
+        # Lerp from max to min as intensity increases, with noise
+        t = min(1.0, intensity / 5.0)
+        base = cfg.asset_swap_max - t * (cfg.asset_swap_max - cfg.asset_swap_min)
+        jitter = random.uniform(-base * 0.3, base * 0.3)
+        return max(cfg.asset_swap_min, base + jitter)
+
+    def get_voice_interval(self, intensity: float | None = None) -> float:
+        """Poisson-distributed interval until next voice clip. Mean decreases with intensity."""
+        if intensity is None:
+            intensity = self.get_intensity()
+        cfg = config.escalation
+        # Mean interval decreases from voice_mean_interval toward 3s
+        mean = max(3.0, cfg.voice_mean_interval / (1 + intensity))
+        return random.expovariate(1.0 / mean)
+
+    def should_fake_calm(self) -> bool:
+        """Roll for a fake calm period."""
+        return random.random() < config.escalation.fake_calm_chance
+
+    def get_fake_calm_duration(self) -> float:
+        """Duration of a fake calm period."""
+        cfg = config.escalation
+        return random.uniform(cfg.fake_calm_duration_min, cfg.fake_calm_duration_max)
+
+    def should_cluster_burst(self) -> bool:
+        """Roll for a cluster burst (rapid-fire events)."""
+        return random.random() < config.escalation.cluster_burst_chance
+
+    def get_cluster_burst_count(self) -> int:
+        """Number of events in a cluster burst."""
+        cfg = config.escalation
+        return random.randint(cfg.cluster_burst_count_min, cfg.cluster_burst_count_max)
+
+    def select_severity(self, intensity: float | None = None) -> float:
+        """Pick a target severity for the next asset. Biased toward current intensity."""
+        if intensity is None:
+            intensity = self.get_intensity()
+        # Normal distribution centered on intensity, clipped to [0, intensity+1]
+        severity = random.gauss(intensity, 0.5)
+        return max(0.0, min(severity, intensity + 1.0))
diff --git a/tests/test_escalation.py b/tests/test_escalation.py
new file mode 100644
index 0000000..4e30602
--- /dev/null
+++ b/tests/test_escalation.py
@@ -0,0 +1,116 @@
+import math
+import time
+
+from server.escalation import EscalationEngine
+
+
+class TestIntensityCurve:
+    def test_intensity_at_zero(self):
+        """Intensity is 0 at start."""
+        engine = EscalationEngine(rate=0.05)
+        assert engine.get_intensity(elapsed=0.0) == 0.0
+
+    def test_intensity_at_40s(self):
+        """Intensity ~1.0 at 40s with default rate."""
+        engine = EscalationEngine(rate=0.05)
+        intensity = engine.get_intensity(elapsed=40.0)
+        assert abs(intensity - math.log(1 + 40 * 0.05)) < 0.01
+
+    def test_intensity_monotonic(self):
+        """Intensity always increases."""
+        engine = EscalationEngine(rate=0.05)
+        prev = 0.0
+        for t in [10, 30, 60, 120, 300, 600, 1800]:
+            val = engine.get_intensity(elapsed=float(t))
+            assert val > prev
+            prev = val
+
+    def test_intensity_never_peaks(self):
+        """Even at 1 hour, intensity is still rising."""
+        engine = EscalationEngine(rate=0.05)
+        at_30m = engine.get_intensity(elapsed=1800.0)
+        at_60m = engine.get_intensity(elapsed=3600.0)
+        assert at_60m > at_30m
+
+
+class TestPhaseParams:
+    def test_low_intensity_params(self):
+        """Low intensity produces slow, subtle params."""
+        engine = EscalationEngine(rate=0.05)
+        params = engine.get_phase_params(intensity=0.5)
+        assert params["morph_speed"] < 0.3
+        assert params["shader_severity"] < 0.3
+
+    def test_high_intensity_params(self):
+        """High intensity produces fast, severe params."""
+        engine = EscalationEngine(rate=0.05)
+        params = engine.get_phase_params(intensity=4.0)
+        assert params["morph_speed"] > 0.6
+        assert params["shader_severity"] > 0.7
+
+    def test_params_are_clamped(self):
+        """Params stay in 0-1 range even at extreme intensity."""
+        engine = EscalationEngine(rate=0.05)
+        params = engine.get_phase_params(intensity=100.0)
+        for key in ["morph_speed", "shader_severity", "voice_frequency", "noise_level"]:
+            assert 0.0 <= params[key] <= 1.0
+
+
+class TestAssetSwapInterval:
+    def test_low_intensity_slow_swaps(self):
+        """Low intensity means long intervals between swaps."""
+        engine = EscalationEngine(rate=0.05)
+        interval = engine.get_asset_swap_interval(intensity=0.5)
+        assert interval >= 5.0
+
+    def test_high_intensity_fast_swaps(self):
+        """High intensity means short intervals."""
+        engine = EscalationEngine(rate=0.05)
+        interval = engine.get_asset_swap_interval(intensity=5.0)
+        assert interval <= 4.0
+
+    def test_interval_has_randomness(self):
+        """Consecutive calls produce different intervals."""
+        engine = EscalationEngine(rate=0.05)
+        intervals = [engine.get_asset_swap_interval(intensity=2.0) for _ in range(20)]
+        assert len(set(round(i, 2) for i in intervals)) > 1
+
+
+class TestVoiceInterval:
+    def test_low_intensity_rare_voices(self):
+        """Low intensity = voices are rare."""
+        engine = EscalationEngine(rate=0.05)
+        # Run many trials since exponential distribution is stochastic
+        intervals = [engine.get_voice_interval(intensity=0.5) for _ in range(50)]
+        mean = sum(intervals) / len(intervals)
+        assert mean > 20.0  # Mean should be around 40
+
+    def test_high_intensity_frequent_voices(self):
+        """High intensity = voices are frequent."""
+        engine = EscalationEngine(rate=0.05)
+        intervals = [engine.get_voice_interval(intensity=5.0) for _ in range(50)]
+        mean = sum(intervals) / len(intervals)
+        assert mean < 20.0
+
+
+class TestSessionTiming:
+    def test_start_sets_time(self):
+        """Starting a session records the start time."""
+        engine = EscalationEngine(rate=0.05)
+        engine.start_session()
+        assert engine.session_start is not None
+
+    def test_elapsed_time(self):
+        """Elapsed time increases after start."""
+        engine = EscalationEngine(rate=0.05)
+        engine.start_session()
+        elapsed = engine.get_elapsed()
+        assert elapsed >= 0.0
+
+    def test_reset_clears_session(self):
+        """Reset restarts the session."""
+        engine = EscalationEngine(rate=0.05)
+        engine.start_session()
+        time.sleep(0.01)
+        engine.reset()
+        assert engine.get_elapsed() < 0.1