diff --git a/apps/web/src/components/condition-picker.tsx b/apps/web/src/components/condition-picker.tsx
index 110049e..13cb28d 100644
--- a/apps/web/src/components/condition-picker.tsx
+++ b/apps/web/src/components/condition-picker.tsx
@@ -20,6 +20,7 @@ import {
 import { useEffect, useLayoutEffect, useRef, useState } from "react";
 import { createPortal } from "react-dom";
 import { cn } from "../lib/utils";
+import { Tooltip } from "./ui/tooltip.js";
 
 const ICON_MAP: Record<string, LucideIcon> = {
 	EyeOff,
@@ -121,25 +122,28 @@ export function ConditionPicker({
 				const isActive = active.has(def.id);
 				const colorClass = COLOR_CLASSES[def.color] ?? "text-muted-foreground";
 				return (
-					<button
-						key={def.id}
-						type="button"
-						className={cn(
-							"flex w-full items-center gap-2 rounded px-2 py-1 text-sm transition-colors hover:bg-hover-neutral-bg",
-							isActive && "bg-card/50",
-						)}
-						onClick={() => onToggle(def.id)}
-					>
-						<Icon
-							size={14}
-							className={isActive ? colorClass : "text-muted-foreground"}
-						/>
-						<span
-							className={isActive ? "text-foreground" : "text-muted-foreground"}
+					<Tooltip key={def.id} content={def.description} className="block">
+						<button
+							type="button"
+							className={cn(
+								"flex w-full items-center gap-2 rounded px-2 py-1 text-sm transition-colors hover:bg-hover-neutral-bg",
+								isActive && "bg-card/50",
+							)}
+							onClick={() => onToggle(def.id)}
 						>
-							{def.label}
-						</span>
-					</button>
+							<Icon
+								size={14}
+								className={isActive ? colorClass : "text-muted-foreground"}
+							/>
+							<span
+								className={
+									isActive ? "text-foreground" : "text-muted-foreground"
+								}
+							>
+								{def.label}
+							</span>
+						</button>
+					</Tooltip>
 				);
 			})}
 		</div>,
diff --git a/apps/web/src/components/condition-tags.tsx b/apps/web/src/components/condition-tags.tsx
index da0418c..0895d5f 100644
--- a/apps/web/src/components/condition-tags.tsx
+++ b/apps/web/src/components/condition-tags.tsx
@@ -19,6 +19,7 @@ import {
 	ZapOff,
 } from "lucide-react";
 import { cn } from "../lib/utils.js";
+import { Tooltip } from "./ui/tooltip.js";
 
 const ICON_MAP: Record<string, LucideIcon> = {
 	EyeOff,
@@ -71,22 +72,22 @@ export function ConditionTags({
 				if (!Icon) return null;
 				const colorClass = COLOR_CLASSES[def.color] ?? "text-muted-foreground";
 				return (
-					<button
-						key={condId}
-						type="button"
-						title={def.label}
-						aria-label={`Remove ${def.label}`}
-						className={cn(
-							"inline-flex items-center rounded p-0.5 transition-colors hover:bg-hover-neutral-bg",
-							colorClass,
-						)}
-						onClick={(e) => {
-							e.stopPropagation();
-							onRemove(condId);
-						}}
-					>
-						<Icon size={14} />
-					</button>
+					<Tooltip key={condId} content={`${def.label}: ${def.description}`}>
+						<button
+							type="button"
+							aria-label={`Remove ${def.label}`}
+							className={cn(
+								"inline-flex items-center rounded p-0.5 transition-colors hover:bg-hover-neutral-bg",
+								colorClass,
+							)}
+							onClick={(e) => {
+								e.stopPropagation();
+								onRemove(condId);
+							}}
+						>
+							<Icon size={14} />
+						</button>
+					</Tooltip>
 				);
 			})}
 			<button
diff --git a/apps/web/src/components/ui/tooltip.tsx b/apps/web/src/components/ui/tooltip.tsx
new file mode 100644
index 0000000..6758417
--- /dev/null
+++ b/apps/web/src/components/ui/tooltip.tsx
@@ -0,0 +1,55 @@
+import { type ReactNode, useRef, useState } from "react";
+import { createPortal } from "react-dom";
+
+interface TooltipProps {
+	content: string;
+	children: ReactNode;
+	className?: string;
+}
+
+export function Tooltip({
+	content,
+	children,
+	className,
+}: Readonly<TooltipProps>) {
+	const ref = useRef<HTMLSpanElement>(null);
+	const [pos, setPos] = useState<{ top: number; left: number } | null>(null);
+
+	function show() {
+		const el = ref.current;
+		if (!el) return;
+		const rect = el.getBoundingClientRect();
+		setPos({
+			top: rect.top - 4,
+			left: rect.left + rect.width / 2,
+		});
+	}
+
+	function hide() {
+		setPos(null);
+	}
+
+	return (
+		<>
+			<span
+				ref={ref}
+				onPointerEnter={show}
+				onPointerLeave={hide}
+				className={className ?? "inline-flex"}
+			>
+				{children}
+			</span>
+			{pos !== null &&
+				createPortal(
+					<div
+						role="tooltip"
+						className="pointer-events-none fixed z-[60] max-w-64 -translate-x-1/2 -translate-y-full rounded-md border border-border bg-background px-2.5 py-1.5 text-foreground text-xs leading-snug shadow-lg"
+						style={{ top: pos.top, left: pos.left }}
+					>
+						{content}
+					</div>,
+					document.body,
+				)}
+		</>
+	);
+}
diff --git a/packages/domain/src/conditions.ts b/packages/domain/src/conditions.ts
index 4bcc006..555613d 100644
--- a/packages/domain/src/conditions.ts
+++ b/packages/domain/src/conditions.ts
@@ -18,63 +18,127 @@ export type ConditionId =
 export interface ConditionDefinition {
 	readonly id: ConditionId;
 	readonly label: string;
+	readonly description: string;
 	readonly iconName: string;
 	readonly color: string;
 }
 
 export const CONDITION_DEFINITIONS: readonly ConditionDefinition[] = [
-	{ id: "blinded", label: "Blinded", iconName: "EyeOff", color: "neutral" },
-	{ id: "charmed", label: "Charmed", iconName: "Heart", color: "pink" },
-	{ id: "deafened", label: "Deafened", iconName: "EarOff", color: "neutral" },
+	{
+		id: "blinded",
+		label: "Blinded",
+		description:
+			"Can't see. Auto-fail sight checks. Attacks have Disadvantage; attacks against have Advantage.",
+		iconName: "EyeOff",
+		color: "neutral",
+	},
+	{
+		id: "charmed",
+		label: "Charmed",
+		description:
+			"Can't attack or target the charmer with harmful abilities. Charmer has Advantage on social checks.",
+		iconName: "Heart",
+		color: "pink",
+	},
+	{
+		id: "deafened",
+		label: "Deafened",
+		description: "Can't hear. Auto-fail hearing checks.",
+		iconName: "EarOff",
+		color: "neutral",
+	},
 	{
 		id: "exhaustion",
 		label: "Exhaustion",
+		description:
+			"Subtract exhaustion level from D20 Tests and Spell save DCs. Speed reduced by 5 ft. \u00D7 level. Removed by long rest (1 level) or death at 10 levels.",
 		iconName: "BatteryLow",
 		color: "amber",
 	},
 	{
 		id: "frightened",
 		label: "Frightened",
+		description:
+			"Disadvantage on ability checks and attacks while source of fear is in line of sight. Can't willingly move closer to the source.",
 		iconName: "Siren",
 		color: "orange",
 	},
-	{ id: "grappled", label: "Grappled", iconName: "Hand", color: "neutral" },
+	{
+		id: "grappled",
+		label: "Grappled",
+		description:
+			"Speed is 0 and can't benefit from bonuses to speed. Ends if grappler is Incapacitated or moved out of reach.",
+		iconName: "Hand",
+		color: "neutral",
+	},
 	{
 		id: "incapacitated",
 		label: "Incapacitated",
+		description:
+			"Can't take Actions, Bonus Actions, or Reactions. Concentration is broken.",
 		iconName: "Ban",
 		color: "gray",
 	},
 	{
 		id: "invisible",
 		label: "Invisible",
+		description:
+			"Impossible to see without magic or special sense. Heavily Obscured. Attacks have Advantage; attacks against have Disadvantage.",
 		iconName: "Ghost",
 		color: "violet",
 	},
 	{
 		id: "paralyzed",
 		label: "Paralyzed",
+		description:
+			"Incapacitated. Can't move or speak. Auto-fail Str/Dex saves. Attacks against have Advantage. Hits within 5 ft. are critical.",
 		iconName: "ZapOff",
 		color: "yellow",
 	},
 	{
 		id: "petrified",
 		label: "Petrified",
+		description:
+			"Turned to stone. Weight \u00D710. Incapacitated. Can't move or speak. Attacks against have Advantage. Auto-fail Str/Dex saves. Resistant to all damage. Immune to poison and disease.",
 		iconName: "Gem",
 		color: "slate",
 	},
-	{ id: "poisoned", label: "Poisoned", iconName: "Droplet", color: "green" },
-	{ id: "prone", label: "Prone", iconName: "ArrowDown", color: "neutral" },
+	{
+		id: "poisoned",
+		label: "Poisoned",
+		description: "Disadvantage on attack rolls and ability checks.",
+		iconName: "Droplet",
+		color: "green",
+	},
+	{
+		id: "prone",
+		label: "Prone",
+		description:
+			"Can only crawl (costs extra movement). Disadvantage on attacks. Attacks within 5 ft. have Advantage; ranged attacks have Disadvantage. Standing up costs half movement.",
+		iconName: "ArrowDown",
+		color: "neutral",
+	},
 	{
 		id: "restrained",
 		label: "Restrained",
+		description:
+			"Speed is 0. Attacks have Disadvantage. Attacks against have Advantage. Disadvantage on Dex saves.",
 		iconName: "Link",
 		color: "neutral",
 	},
-	{ id: "stunned", label: "Stunned", iconName: "Sparkles", color: "yellow" },
+	{
+		id: "stunned",
+		label: "Stunned",
+		description:
+			"Incapacitated. Can't move. Can speak only falteringly. Auto-fail Str/Dex saves. Attacks against have Advantage.",
+		iconName: "Sparkles",
+		color: "yellow",
+	},
 	{
 		id: "unconscious",
 		label: "Unconscious",
+		description:
+			"Incapacitated. Can't move or speak. Unaware of surroundings. Drops held items, falls Prone. Auto-fail Str/Dex saves. Attacks against have Advantage. Hits within 5 ft. are critical.",
 		iconName: "Moon",
 		color: "indigo",
 	},