Dear Three Rings Design.
Honestly, the completely wasted materials known as Valestone and Moonstone is very present to me. Perhaps you could update the game with new battle sprites to compensate for the lack of purpose for these two terrible minerals.
For example:
Moonstone: The Moonstone could be used for a sort of wolf battle sprite, similar to the wolver enemies that already exist in game. I feel this sprite would specialize in close combat, in sharp contrast to the dragon's projectile attacks. I feel this would add more variety to the battlesprites and make them more useful for different players. For example, i play with a sword and gun, so a close combat pet would probably be very useful to me.
Valestone: Now, me and my friends have been pondering this for a short while, and i believe that the valestone could possibly be useful for some sort of slime or lizard like battle sprite, something with a quirky play style that benefits the quirkier players that you can see ingame. A lizard battle sprite would potentially be able to steal a material from an enemy or even just stun an enemy with its tongue, allowing people who often enjoy playing as a thief like character in other games to benefit more greatly by hindering their enemies or getting more materials. Of course, this would have to be balanced accordingly. I feel like a slime battle sprite would potentially be a whittle-down-over-time, similarly to the already present ghost battle pets. Which brings me to my next point:
Ghost battle pets: Now, THIS. THIS has potential. I know you wanted the ghost to be a status effect pet, i really do, but one REALLY cool thing that i think this pet should be able to do is temporarily control an enemy to attack other enemies, because honestly, who hasn't wanted to start a war between their enemies before? I feel like this would be their last ability, and the ghost would be able to keep or slightly tweak it's other abilities.
The Cat battle pets: Pretty good across the board, but the heart attack could do with an area of effect upgrade. From what i've seen from the preview i got the heart attack is pretty useless, especially since the cat pet shoots a ranged beam.
Guild Halls: Now then! I love what you've done so far with the guild halls, and i know they're not your first priority, but honestly these could do with an upgrade. For a start, featured rooms should either be able to be renamed or have their flooring changed (where applicable) AT LEAST. Machines should be buyable aswell as merchants, but i feel there should be a penalty of some sort to doing so, such as either upkeep or being bought with energy! It'd add a lot more customization to the guilds and make it even more fun to hang out there instead of it being just a passing glance.
Yours Sincerely,
-Cairyth.
The problem with adding new sprites is kind of two-fold.
A: They'd probably have to add in 2 new missions dedicated to the new sprites, which wouldn't work well in the whole mission select layout.
B: All the people who already have a sprite but want one of the new ones instead might feel ripped off. At least when they were first introduced nobody had sprites so everyone just played those four missions and got their sprites, no big deal.
Personally, I feel like a better solution is to find some other use for Valestone and Moonstone (cough multi sprite foods cough my suggestion from ages ago cough).
Uh, Maskeraith already has all three of its abilities set in stone. One of the ults for Hexing Haze (the third ability) causes random status, and the other one spawns ghosts that attack enemies, so your ideas are kinda covered.
Heart Attack is upgradable. From what it sounds like, you've only played the preview mission, and have never really played with sera much, but there is a range upgrade, and at three upgrades the range is pretty darn big.
What exactly do you mean be "machines should be buyable"? It's actually been forever since I've seriously played, but I don't know what you mean. I do like the idea of extra customisation to guild halls though (silver guild update? no? anyone?).
Side note: actually SK is owned by Grey Havens (GH) now.