I like the game (for now), there is a strategic aspect, and it plays quickly. You can get decent cards w/o spending real $$$, or *ANY* money, but luck is a big factor.
Events change how games play & which cards are more effective. Multiple events can run simultaneously.
You make one 15 card deck, with one purchaseable upgradeable hero. You can keep up to 100 cards in storage and as many heroes as you can afford, but they are not very relevant to gameplay (unless you sacrifice them to upgrade your other cards).
Free to Play (F2P) and Pay to Win (P2W) are generally hated by mobile gamers because the gameplay suffers from the greed, and a few (often unskilled) players win a lot by spending a lot (often hundreds of $). Spellstone is definitely one of these games.
multiple currencies (gold, gem 'shards' (premium), and magic dust), energy timers, PVP 'contracts' (essentially another timer), upgradable cards, fusion cards, and no way to simply pick/purchase the card(s) you want. Meh.
I can't see what cards opponent has played when countdown is on. #DesignFail? Seems like an idiotic mistake for such a well-made, sleek, and fast playing game.
No chat in PVP, little incentive to interact with other players, and option to autoplay (ie autogrind) at 3x speed w/o paying attention (which to me is similar to not having much fun, but playing as more of a 'grinding chore').
Besides events, there are special packs which let you pay Shards (premium currency) to draw one random card from a preselected grouping of very high powered Legendaries, some epics, and some rares. This is aa serious P2W money sink, and you generally won't earn enough Shards to draw w/o paying $$$.
So I keep playing this game (addictively), and I can see my burnout on the horizon. So why do I like this game? Its silly, but I like to beat paying players with my free cards.
Aside from the Card Battling, most of the game is a storefront trying to get players to pay money to buy shards (premium currency) for Legendary cards.
Note: Kongregate has another game, Tyrant Unleashed, that plays very similarly to this game but is set in a cyberfuture sci-fi war setting. In fact, this is almost identical to Tyrant Unleashed, but in a Fantasy genre & w/comic art.
There are three factions (Chaos, Wyld, and Aether), and a variety of skills. There are also a few specific creature types (Angels, Frogs, Elementals, Dragons, Undead, etc) that can be affected by Skills.
Choosing & upgrading cards in one faction is key to success, or boosting general cards w/o faction-focussed powers. I suggest picking a faction you like based on art or powers, or draw cards & decide when you draw a great epic card, and beef up your preferred cards in that faction.
(I chose Wyld when I drew 'Rhythm od the Wyld" and "Werewarg", two solid Wyld cards. Werewarg is definitely OP, while Rhythm is merely a very strong Epic.)
There are a range of skills, too. Some are better than others, IMO, but the key is matching them well.
Skill list: Armor, Barrier, Bolt, Dualstrike, Empower, Enhance, Fervor, Freeze, Heal, Hex, Invisibility, Legion, Pierce, Poison, Scorch, Siphon, Vengeance, Weaken. (So far, I haven't seen Legion or Fervor, but they were listed in the Wikia so I included it here.). Most skills have a number after, and some have " all" (as in 'Heal All Wyld'). Obviously, "All" should make players excited -- improving your entire lineup vs one card is invaluable.
Your hero's abilities need to support your deck's skills. This can be tricky.
I tend to focus on Defensive -- Armor, Heal, & Empower. I have a few creature cards with Poison & Siphon, Bolt, Enhance, and Invisibility. I think Barrier and Freeze will get added as soon as I have good cards with those options.
In gameplay, I lead with armored cards unless the opponent has a pierce. My strategy is to have more cards out than my opponent, so stronger cards need to be in front & weaker support cards in back. If my strong cards can hold, they tend to keep my supports around longer.
Offensive skills that are challenging (esp in combination) include Bolt, Hex, and Scorch. Most effective against my deck is Pierce, Siphon, Bolt, and Weaken.
The strongest skills (they are fine 'stand alone') are Armor, Siphon, Bolt, & Vengeance. Armor is like extra HP every round. Bolt & Vengeance seem to bypass armor, while Siphon is a self-heal. Freeze is actually powerful, but nerfed by not operating every turn (same w/Dualstrike).
I think these skills are wastes -- Poison, Scorch, Pierce, and Dualstrike -- but in certain scenarios they could be helpful, namely fighting a big HP Siphon/Armor card.
Lastly, some skills are in effect while your card is counting-down to activate: Armor & Vengeance. I'm uncertain about Invisibility.
Mistakes I've Made:
Unless you pay $, you will have limited dust. Save it for your rares/epics/legendaries, and your heroes. (I upgraded & fused a few commons, and that probably will hurt me in the long run. **Update: you get refunded some dust when you recycle upgraded cards, but far less than 80%.)
Having a 0 countdown card can be useful as the last card in your lineup, if you always have a 1card advantage. Another option is playing them in front of a big countdown card. Otherwise they are generally too weak to be useful.
Having a card with a useful skill can help a lot. Having healers in front getting clobbered generally sucks, but if you have 4-5 thrn they may last for awhile before getting dusted.
Frog challenge: frogs avoid 2pts of damage means frogs are waaay stronger now.
Elemental challenge: elementals get +2 attack means elementals hit harder. (My Nix Elemental with Siphon2 & Poison2 becomes very strong.)
I feel I've had enough & now feel obligated to play, so its delete time.
For my fond memories, my final deck was Wyld faction:
Storm Dragon (Chaos)
Rhythm of the Wyld
Scythe Demon (Chaos)
Nixfire Elemental (Chaos)