MArcomage

"Discard chosen card and it's neighboring cards. Summon card which has all discarded keywords."

Your note supposes that there exist cards for every combination, but this isn't the case. (Consider most keywords combined with Flare Attack or Rebirth -- such cards don't exist.) You have to consider what would happen then.

Similar concepts have been proposed, and the discussion always comes down to whether it could be used to easily turn Wildfire gem into Phoenix. As long as this card either avoids this or requires the exact combination of Wildfire gem and Fire elemental (which might not work anyway since the latter has Enduring), it shouldn't be an issue.

There might be other Rares that would be relatively easy to summon with this, but since this is Uncommon and requires careful hand manipulation to pull that off, it's probably balanced.

Removed choosing so it's much more situational.
As per phoenix - he is very easy to summon with feather, and the cost does not differ that much. It's harder to play him than summon.

Phoenix feather is unique in that the condition to play it for the summoning effect is to create a situation in which you would never want to immediately play Phoenix. That limitation doesn't exist for the previously proposed cards that replace based on keyword.

I like this revision to Merge. It sounds very interesting and has potential in any keyword deck. I'd still like to see in what situations you can "know" what you're going to draw and perhaps design a deck with this in mind. I could see adding a Dragon to just about any themed deck giving the potential to pull a specific Rare with lucky hand shuffling or careful use of Magic portal.

Well If you got phoenix from feathers, you've got to play another one, or common flare before it.
But if you waste your common flare to make a phoenix, you got to wait for another one.

I did say that it wasn't a problem in this case. It was an issue with other proposed cards, but this one has more specific requirements.

Interesting idea. The only thing I don't like about it is that, more so than any existing card, it requires an encyclopedic knowledge of all cards in the game to use effectively.