Sorry @epicflygon and @alexx55, but neither of those are the answers.
Hint: Though itās not a card from either of these factions, itās best known for itās use in either Abyssian or Magmar decks
Sorry @epicflygon and @alexx55, but neither of those are the answers.
Hint: Though itās not a card from either of these factions, itās best known for itās use in either Abyssian or Magmar decks
Ephemeral shroud.
dioltas?
ajdnsduafgndf
Your General gains +3 Attack. Whenever your General destroys a minion, summon a 3/3 Blazing Spine Wall on that space.
Relic, sacrifice, undone, mountains, renewed, testament, lain down(relics are destroyed)
It fits the riddle. 
Interesting, I was thinking of lain down as not being played and relic not as the physical interpretation, but rather as an adjective.
Though the fact that itās a non-token minion auto-disqualifies white asp, Iām curious as to where you saw mountains in it (an asp is a snake and blazing spines are like wooden barricades)
@epicflygon, @loliconartist - Nope
(Weāre at 10 guesses folks, the reveal comes at 15!)
Cryptographer?
Since he is widely used in Lilithe/Maehv and Vaath/Ragnora (even sometimes in Starhorn), while other factions that use him are Vanar (Faie and rarely Kara) and Songhai (Reva)
Regretfully no, cryptographer doesnāt match the sacrifice line.
(Weāre at 11 now)
Could it be Grimes?
Nope, sorry but Grimes is in fact not the answer to this particular puzzle (I wish it were though).
(12)
White Asp spawns a Blazing Spine(mountain) on minion kill
Huh, I always thought blazing spines looked more like wooden barricades to me:

Azure horn Shaman
Reasoning:
Rel
Azure horn sounds like a relic
a very situational play, hence why rarely used
Dying wish
Azure sounds like Sapphire, a jewel, found in mountains?
Buffs HP
Ohh, that guess would be near perfect if not for the forgettance lines (which are reference to an inherent part of the minions ability).
Seriously though, great reasoning on that! I was nearly tempted to call that an alternative answer to the riddle
(13)
Is it that everyone forgets his ability orā¦
Could this be Ironclad by any chance?
Nope (14)
Last Hint!: The unforgotten portion refers to a pool of some kind.

Grimes?
What have I done, I just used the last guess.
you didnt, i guessed it
Aaand thatās NOT THE RIGHT ANSWER (hexk, it was even preciously guessed). C
The minion this time was Keeper of the Vale!
Itās part of the core set and reached itās peak power/noriety before the present.
References how a certain condition must occur before people would play it.
A minion should die before people would play Keeper.
Unforgotten is reference to the āminion poolā that Keeper pulls itās summons from. Beneath mountains are valleys (vale means valley). Beneath also couldāve referenced underground which could help lead you to thinking death.
Keeper resummons dead minions, making them new again
Valleys are made via glaciers/rivers carving their way through mountains so the mountains are proven to not be invulnerable. Dead minions arenāt strong minions!
Hmm, that mountain refference was very cryptic, too cryptic even