Recs.
Updated
SpecsUpdate
Pros
Pro Sweet spot between MtG and Hearthstone
This game is not as complex and deep as MtG, but still it requires a lot more of strategic thinking and deck-building skills than HS. At the same time, a game of Eternal can usually be finished within 10 minutes.
Pro Very friendly to free to play players
Rewards for playing vs AI help new/inexperienced players not get obliterated in constructed, and keeping cards you draft helps you build the collection you want without simply opening packs.
Pro Frequent balance changes and diverse metagame
Devs are not afraid to frequently buff or reasonably nerf cards to balance the metagame.
Pro Very fast dev response to bugs and issues
Devs are active in discord channel and official forums.
Pro Beautiful and user friendly UI
The PC UI is incredibly smooth, and although the mobile/tablet UI is a little sluggish, it is still better than some other games.
Pro Community is mostly kind
Eternal's subreddit and discord server tend to be mature and respectful. People you friend in game are more likely to talk about how cool your deck is than to give you salt.
Pro Regular updates and content
Updates and promos once a month every month since open beta.
Pro Pack system is generous
Instead of trading cards with other players, there is a recycling/crafting system for handling duplicate cards and obtaining cards you want. Every pack gives you "shiftstone" on top of whatever cards you open, making it easier to craft expensive cards than in other games.
Pro Card art is attractive and inclusive
Art is simpler than Magic's, but leans toward realism over cartoons. Women are represented in a respectful and diverse way.
Cons
Con It is a MTG clone minus any skill requirements
It has almost no way to out maneuver your opponent. Your draws decide the game. The screw/flood seen in MTG is made worse with the horrible design choice to use 75 card decks.
Con Mana screw happens
There are elements in the design to help prevent it, but you will still randomly lose games to drawing little or too much mana.
Con Visually lacks in flair and drama that might be appealing to players of other games
Voice-overs for many cards were recently added in a patch, but only one game board and no interactions between particular entities (calling out relationships or rivals) can make the game feel "stale" or "bland" compared to the level of polish of, say, Hearthstone.
Con Requires waiting for a full board
Most of the time you have to wait to fill your board with the correct units before attacking. This makes the game quite slow and clumsy.
Con Not a mobile-friendly game
Best played on a PC or a tablet. Playing on a phone can be difficult as it's a direct port from PC so text and images can be tiny. Not a problem if you're familiar with the game, but new players it will be frustrating.
Recommendations
Comments
Flagged Pros + Cons
Con It is a CCG not a TCG
Any money / time you invest into Eternal is locked into the game. You can never get it back out or build actual value in your collection like you can in a trading card game.
Out of Date Pros + Cons
Con Casual play not yet implemented
Casual mode is planned but not yet available until the player base expands (presumably once the game leaves beta).
Con Original campaign is rather boring
The original campaign (although generous) is very boring and doesn't show enough advanced mechanics of the game.