DPsycho wrote:
your opponent is able to keep track of where you have dragons and eggs by watching whether your gems are doubled
If
1) You will play dragon card
and
2) You have another gragon card.
If you have few dragon cards in your deck, you can play other cards and hide egg card up until then you will use it.
Revealing of dragon egg card doesn't follow game situation univocally in most cases and destroys suddenness.