Reply: Spirit Island:: General:: Re: Luck and probability help

by conorchinitz

Some adversaries do weird stuff to the setup of the Invader deck, but I'll ignore that and answer the question for the typical setup only.

The short answer is, on turn 3 you have a 20% chance of drawing an Invader card that matches the one you drew on turn 2. And that's it, I believe.

Once you get to the stage III cards, you can more easily get the same terrain showing up on two cards in a row, since each card has two terrains, but you can't draw exactly identical cards because each Stage III card shows a unique combination of terrains.

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The calculation works as follows. The cards in each Invader stage are all unique within their stage. Stage I has one of each terrain type, with no duplicates. Stage II has one of each terrain type, with no duplicates, plus the Coastal Lands card. And Stage III has one of each combination of two terrain types, with no combination duplicated. That means the only time you could ever draw the exact same card twice is when you draw the first Stage II card--it could match the last Stage I card that you drew.

There are five Stage II cards (one four each of the four terrains, plus one Coastal Lands card). Therefore, there's a 20% chance that the first Stage II card you draw is any specific one of the five, and therefore there's a 20% chance that it matches whatever the last Stage I card was.