Work TypeWork cards remain in play each Clean-Up until they have been worked sufficiently as indicated by the Work card. During Clean-Up, a card with "-3 Work-" on it is only discarded if it has been worked 3 times.
During your Action phase whenever you could play an Action, if you have any Work cards in play that have not met their Work count, you may "Work" that card by spending a +action and placing a Work token onto the card. You may work any number of work cards as much as you want in a turn (so long as you have +actions to spend and the card can take more work). Work tokens remain on the card until is discarded during a Clean-Up phase.
Builders
Types: Action, Work
Cost: $2
+$2.
-2 Work- When you work this, +1 Buy.
Heir
Types: Action, Victory, Work
Cost: $4
+4 Cards. Reveal your hand and discard the revealed Victory cards.
-3 Work- Worth 1VP per work token here.
Metropolis
Types: Action, Work
Cost: $5
While this is in play at the start of your turn: +1 Action.
-1 Work- When you work this, reveal your hand. +1 Card per differently named card revealed.
Builder is like a Woodcutter, but you need to spend +actions for the +Buy. It could provide early economy and then sit out of your deck until you need the +Buys if you wanted.
Heir is a powerful draw that requires you to spend 3 extra +actions to get it back into your deck. Or just use it as a one-shot and put +actions into it for up to 2VP (an Heir with 3 Work tokens on it will be discarded the Clean-Up before the game ends and is therefore worth 0VP).
Metropolis can sit in play like a cross between
Hireling and
Barracks. Pop that +action now for a draw with a bunch of variety. Pop it later for a game-finishing turn.
Fundamentally, these are similar to Reserve cards. Their ability to be triggered multiple times, and the fact that they remain in play makes them more flexible and provides different effects, considerations, and combos. Oh, and you have to spend Actions to work them instead of having different calling conditions, doodleduh.
EDIT: Clarifications.