Secret: When your hero takes fatal damage, prevent it and become Immune this turn.
Ice is nice, and will suffice!
 How to get
|Golden Ice Block||1600||400|
Can be very effective as an endgame surprise and can be a clutch game saver, giving you one more guaranteed turn.
Note that Ice Block will be triggered in response to any attack (during the opponent's turn) that would deal fatal damage to the mage - the mage's health will then by frozen at its current value. For this reason it is generally desirable for opponents to attempt to get the mage's health as low as possible before triggering damage. In this way, when the mage loses Immune at the start of the next turn, they will have a minimum of health remaining.
Since this secret will only trigger once your health gets below 1, playing this card with the Ethereal Arcanist is a fairly strong mid-game combo, giving the minion continual +2/+2 boosts.
As with all secrets, it should be noted that Ice Block will not activate on the controlling player's turn, meaning that sources of damage such as Fatigue, Mad Bomber or a paladin's Eye for an Eye on the mage's turn are capable of destroying the mage despite the presence of an unactivated Ice Block.
Ice Block is a mage spell from World of Warcraft. It encases the mage in unbreakable ice for 10 seconds, but prevents the mage from moving or acting for the duration. Unbreakable by all but the most powerful spells, the ice block renders the mage completely immune to all damage, and other hostile effects. It is commonly used in PvP to frustrate and delay opponents, as well as to give the mage time for their cooldowns to recover, at which point the mage may try to escape, using spells like Frost Nova and Blink to make their getaway. It can also be useful to buy time until a healer can get to you, or can be used immediately after activating a heal over time effect to allow the mage to 'stealth-heal', invulnerable from further attack. Similar to Hearthstone's version, mages can also use it specifically to avoid damage from a particularly powerful attack.