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Frosthaven outpost attack calculator
Type the attack value off the event card and your current defense value. The calculator runs the town guard deck and tells you how often the building comes through.
| Card | In deck | Defends at 15 vs 30 |
|---|---|---|
| +0 | 6 | no |
| +10 | 5 | no |
| +20 | 1 | yes |
| −10 | 5 | no |
| −20 | 1 | no |
| Success (always defends) | 1 | yes |
| Wreck (always wrecks) | 1 | no |
Exact odds from the starting 20-card deck. Town guard perks (building 90) change the deck, so a late campaign drifts from these numbers.
How to use it
- Copy the attack value from the event card.
- Enter Frosthaven's total defense value from the campaign sheet.
- Add any soldiers you plan to spend, and the reduction each one gives.
- Read the odds of the defense check passing before you draw.
What the defense value is
Frosthaven's defense starts at 0 after scenario 1 and then moves with the morale track. Only the modifier printed next to your current morale applies — they are not cumulative.
Each wall you build adds 5 permanently. Events and buildings can add or take away more, which is why the campaign sheet has a running total rather than a fixed number.
How an attack resolves
An attack event lists an attack value. Each targeted building gets its own defense check: draw one card from the town guard deck, add its bonus to the total defense value, and the check passes if that total meets or beats the attack value.
The starting deck is 20 cards: six +0, five +10, one +20, five −10, one −20, one Wreck and one Success. Two of them override the arithmetic — the Success card always defends the building, and the Wreck card wrecks it whatever your defense is.
That is why a defense value of 15 against an attack of 20 still fails more often than it feels like it should: you need +10 or better, and only seven of the twenty cards get you there.
Soldiers
Before drawing, as long as the Barracks is not wrecked, the party can spend any number of soldiers. Each one lowers the attack value by an amount set by the Barracks level: 5 at level 1, 15 at level 2.
Spending at least one soldier also gives the check advantage, so you draw two cards and keep the better one. With the Barracks wrecked you cannot spend soldiers and the check has disadvantage instead.
Soldiers are spent per building, not per event. Two attacked buildings means deciding twice, and the soldiers you used on the first are gone for the second.
Where the odds come from
The numbers on this page are the exact outcomes of drawing from the 20-card deck, not a simulation. Without soldiers the pass rate is simply the share of cards that reach the attack value; with advantage it is worked out over every pair of cards the deck can give you.
The deck changes during the campaign as town guard perks are added at building 90, so a campaign that has upgraded the deck will drift from these odds. Once your deck is no longer the starting 20, treat this as the baseline it started from.
Questions
- What is Frosthaven's starting defense value?
- Zero, before the morale track and before any walls. After scenario 1 the morale modifier moves it up or down, and each wall adds 5.
- Do soldiers add to defense value?
- No. Soldiers lower the attack value instead, by the Barracks amount each, and they give the check advantage. Defense value is what you add the card to.
- Can a defense check ever fail with a high defense value?
- Yes. The Wreck card wrecks the building regardless of the numbers, and a −20 can undo a comfortable defense value. High defense makes failure rare, not impossible.
- Is it worth spending one soldier for advantage?
- Usually yes. One soldier both cuts the attack value and makes you draw two cards, and the odds on this page show the difference the two changes make together.
Other Frosthaven calculators
Numbers last checked 2026-10-20. Sources: Frosthaven rulebook (Appendix D, scenario level table, town guard deck) and the official Frosthaven FAQ.