Future Sight possible spoiler card:
Keldon Megaliths
Land
Keldon Megaliths comes into play tapped.
: Add

to your mana pool
Hellbent -

,

: Keldon Megaliths deals 1 damage to target creature or player. Play this ability only if you have no cards in hand.
#170/180
Although there is the massive downside of this card coming into play, it seems like if the testing supports my first guesses, that this card will be incredible in Ubastax. Almost since the inception of what we now call Ubastax, there have been 4 Barbarian Rings maindeck. This was to kill the following:
Goblin Welder
Dark Confidant
Kataki, War's Wage
Ashen Ghoul/Ichorid/Nether Shadown
And a host of other creatures. Hell, this is why Ubastax would often play Granite Shard in the SB and occasionally maindeck. Now, with the ability to put it into a land, the single greatest downfall of Granite Shard, the fact that it couldn't be used with Null Rod, has now been overcome. With a slightly steeper activation cost of

and the need for Hellbent to actually make it work, the questioni would have to be would this be able to fit into Ubastax as a 1-3 of.
Personally, I am currently leaning towards yes. With or without smokestack or thresshold, Ubastax can often easily get rid of its entire hand. Between Bazaars and Uba Masks making sure you keep an increasingly lower hand size, this can be a deadly weapon to take care of all of those threats, often faster than Barbarian Ring can get online. This also doesn't require a crucible to continually destroy creatures.
While I wouldn't replace Barbarian Rings with Keldon Megaliths, a 3/2 combination of Rings/Megaliths might be something for me to think about, especially with the Megaliths producing

mana regardless.