The game has four groups of Enemy Cards:
During Setup, the Enemy Cards should be separated so Act I cards and cards without Act number make up the initial Enemy Card deck (kept next to the Game Board, while Act II and Act III cards are keep in two separate piles, which will later be shuffled into the Enemy Card deck when the corresponding Act begins.
If the Enemy Card deck runs out of cards, shuffle the discarded Enemy Cards to make a new Enemy Card deck.
Practical note: since spawning enemies happens differently for On Deck enemies and for enemy ships, it makes things simpler if the enemy ship cards are kept in a small separate deck; and when an enemy ship card is discarded, to shuffle it directly into that separate deck instead of putting it in the general enemy card discard pile.
The On Deck enemies are miniatures that are spawned in the On Deck area of a player's Ship Board. Their Enemy Cards have three numbers along the left side:
A fourth number is placed in a diamond immediately to the right of the name at the bottom of the card; this is a Roman numeral indicating which Act this enemy belongs to.
On the right side of the On Deck Enemy Card, there are special abilities, showing die faces indicating dierolls are needed to trigger the ability, and a text describing what the effect of the ability is.
On the left side of Enemy Ship Cards, there is a health and dice value like the On Deck Enemy Cards, but they don't have a Spoils reward, and they don't have an Act number next to their name.
On the right half of Enemy Ship Cards is a number in a circle, giving the Engagement Range (meaning how many hexes away on the Game Board the enemy ship can spot player ships), an arrangement of hexes indicating in what direction from the enemy ship that it can before attacks. In the lower right corner of the card is the destination for the enemy ship, used to determine the Enemy Ship Movement.