Hazards are obstacles that make a level more difficult. Each Hazard has a different mechanic to get past it.  You can also use Boosters to help clear most Hazards. Some Hazards do not have corresponding Boosters. These Hazards have unique requirements you must achieve to remove them or to receive their reward. Finally, there are some Boosters that help you win levels and earn more stars that do not directly interact with Hazards.

To view your Booster inventory you can click the orange triangle in the upper right hand corner of the Events & Quests progress screen, after completing a level. Ex:

Hazards with Boosters:

Trap & Trap Torch:

Play 2 cards from you to remove this hazard OR play a Trap Torch Booster.

Shark/Bait & Shark Hook:

Find the bait to clear the Shark Card OR play a Shark Hook.

Bomb & Bomb Defuser:

Play a card on the Bomb before time runs out and the Bomb explodes OR play a Bomb Defuser.

Big Wave & Wave Breaker:

Find a match to stop the waves from stealing card OR play a Wave Breaker.

Frost & Defroster:

Find the Defroster card in the stockpile to melt the ice OR play a Defroster.

Hazards without Boosters:

Treasure Totem:

Sacrifice cards to the totem and complete the level to unlock the treasure.

Crystal Card:

Sacrifice one card of each symbol (Clubs, Diamonds, Hearts & Spades) to earn the prize.

Butterfly Vault:

Free the Coin Butterfly with the correct card. Unlock card changes with each stockpile use.

Boosters without Hazards:

More Time:

Play this Booster to add 30 Seconds to your level Timer to improve your chances of earning the Speed Star for that level.

Streak Doubler:

Play this Booster to double your Streak Bonus to improve your chances of earning the Streak Star for that level.

Magic Eye:

Play this Booster to magically highlight the next playable card in the Tableau for the entire duration of your time on that level.

Red Star Booster:

Activate this Booster in the Red Star Leaderboard menu to earn 2x Red Stars for 3 hours after activation.