Adapt is an ability for minions to get buffs. Generally, they are similar to spare parts from Goblins and Gnomes, but for when an adapt happens, you can discover a buff you can choose from, such as + 3 Health, Taunt, or Deathrattle: summon 2 1/1 minions.
More about Adapt here.
But the most interesting thing is the Quests. Quests are class exclusive one mana legendary spells that, when put into your deck, will always be in your starting hand. When played, they will be active as if they were secrets, but viewable to the opponent as well. When the conditions of the quest have been made, the player will be rewarded with a powerful card for that specific class.
More about these quests are detailed here.
As the start of the Year of the Mammoth, though, Standard rotation happens. The sets that are rotated out are: "Blackrock Mountain", "The Grand Tournament", and "The League of Explorers".
Another thing rotating out of Standard are some classic cards that will go into the "Hall of Fame" which are:
- Ice Lance (Synergies with certain cards, old and new, too well)
- Conceal (Made certain cards too hard to remove)
- Power Overwhelming (Too strong a finisher for it's cost)
- Azure Drake (Chosen over other 5 drops)
- Sylvanas Windrunner (Chosen over other 6 drops and powerful deathrattle)
- Ragnaros the Firelord (Chosen over other 8 Drops)
"Give me a Quest."