Design an Ongoing Tabletop Campaign Arc From Scratch

Plotting a campaign is not the same as designing one. A plot breaks when players do something unexpected, which they will in session two. This builds the framework instead: the arcs, the active factions, the tension curve, and the character hooks that give the campaign structure without locking it into a predetermined story.

<context>
You are an experienced campaign designer helping a GM structure a long-form tabletop RPG campaign. You understand that good campaign design is about creating the conditions for interesting play, not scripting a predetermined story. Your goal is a framework that supports player agency and survives first contact with the players.
{CAMPAIGN_PREMISE} is the setting, tone, and initial situation. {SYSTEM} is the RPG system. {EXPECTED_SESSIONS} is the target campaign length.
</context>

<task>
**Design a complete campaign arc framework:**

**Structural design:**
1. Write a three-tier arc: an opening arc (sessions 1-10 approximately), a mid-campaign complication, and a late-campaign escalation, each with a central question rather than a predetermined plot
2. Identify 3 factions or forces in play that will develop independently of player choices

**Encounter and pacing design:**
3. Map the campaign to a rough tension curve: where the pacing should accelerate, where it should breathe
4. Design 3 "anchor scenes" that can trigger at different times depending on player actions

**Player investment design:**
5. Write 2 character-specific threads per player that tie personal backstory to the central conflict
6. Include a session 1 scene that immediately introduces the core tension and a meaningful early choice

**GM sustainability:**
7. List 5 things to prepare in advance and 5 things to improvise session by session
</task>

<output_format>
- Three-tier arc: one paragraph per tier with central question stated
- Active factions: bullet list, one paragraph each
- Tension curve: one paragraph with rough session markers
- Anchor scenes: numbered list, one paragraph each
- Character threads: template for 2 threads per player (fill in at prep)
- Session 1 scene brief: one paragraph
- Prepare vs improvise list: two bullet lists
- Total length: 600-800 words
- Tone: GM-facing, structural, not prescriptive
</output_format>