You often want to aim for a smooth mana curve that allows you to play spells consistently throughout the game
In an absolute sense, the expected value is solid at the moment, probably significantly better than most people think, although declining prices and the variance of the set mean that opening the set is certainly a risk, since most of the set's value is concentrated in a few extremely expensive (and rare) cards
We are keeping the description general here since the printed treatment rewards being seen directly rather than recalled from a summary
While other card types can be answered as long they can be chained (Mainly Quick-Play Spells and other Traps), Counter Traps are Speed Spell 3, the highest tier of activation which answers the below Speeds and can only be negated by others in the same tier
they usually give you bonus points for having a lot of cards of a single color, but if a player is lucky enough to collect all four Mermaids in their hand in the same round, they win the game automatically