Here is a magic set I made, it has some key abilities (some of the names are pretty cheesy):
Yes, I realize some cards are completely borked out of their mind, but I appreciate the input
silent strike: Creatures that block this creature without first strike don’t deal combat damage. the compiler I used for the spoiler didnt realize that mythics are mythics, so it just put it at commons. It should be pretty obvious though.
Primal Superiority: Cost, T: Attach this creature to another target creature you control. Attached creatures cannot attack or block. If the creature that this creature is attached to leaves the battlefield, unattach this creature. Use this ability only as a sorcery.
Insurgency: At the beginning of your upkeep, if this creature did not attack or block since your last turn, including that turn, put a insurgency counter on this creature. Do not count turns in which this creature had summoning sickness.
704.5q If a creature is attached to an object or player, it becomes unattached and remains on the battlefield. Similarly, if a permanent that’s neither an Aura, an Equipment, nor a Fortification is attached to an object or player, it becomes unattached and remains on the battlefield.
Silent Strike: There are only 2 creatures with first strike in the entire set to counteract Silent Strike.
Command the Beasts: Name sounds Green, and the rules text is ambiguous. Did you mean 'creatures with objects attached to them'?
Swarm of Locusts: This card is pretty terrible. It involves jumping through hoops to get a bunch of 1/1 tokens that won't last more than 1 or 2 turns.
Vampire Beastvendor: You need to add a 'reveal' clause because the card searched for has a specific quality. Feels like a green card mechanically.
Garruk, Wielder of the Seal: Ultimate doesn't feel Green at all - land destruction on that scale is normally reserved for Red.
Seal of Duermis: This is a 3 cc artifact that would typically ramp up your mana by 3-4 depending on when you used it. This may be problematic.
Confinement Ring: See Faith's Fetters for the appropriate wording. Feels more like a White card.
Mind Annihilation: Almost always worse than Dissipate. Also, counterspells that don't actually say 'counter' on them tend to lead to arms races.
Aquamiran Seer: You will always be able to draw 2 cards of this on each of your turns because of the way priority works in Magic.
Fallout: Terrible card. Specifically hosing basic lands is poor design, and mass land destruction is either White or Red. Card name sounds like it belongs in either of those colours as well, not Black.
Silverblade Striker: A bit complex for a common.
Savage Vampire: Undercosted. The Titans are not a benchmark to cost creatures by. Even Green doesn't have a non-Titan creature that matches this in efficiency.
Hoarding Researcher: You're never going to attack with it (0 power) or use its ability after it blocks (1 toughness) anyway, so why not just automatically put a counter on it each of your upkeeps?
Master Revoker: Should just say 'Shuffle target creature into its owner's library'. This effect also effectively destroys the targeted creature, and isn't really Blue.
Stockpiler Jones: Way overcosted. 6 mana buys you 4 cards from Mind Spring. This creature needs to survive and takes 4 turns to do the same thing.
Lunar Melody: The randomness of the effect makes it feel Red. Undo is a much cleaner effect, but maybe bounce is supposed to be weaker in this set?
Time Legacy: This really shouldn't be a common. Rare caliber.
Shelira of the West Winds: 'tap up to'
Guardian of Aquamira: You need to define X.
Moondust Drake: 3U to cast 2 sorceries or instants for free is broken. Even getting a single Cruel Ultimatum off this would be crippling for your opponent.
Lightning Blast: Name is already taken: Lightning Blast, and X needs to be defined.
Valdarenan, Heart of Magma: Card should not be a common.
Fireblade Assassin: Not Red at all. Mechanically Black.
Turn to Cinder: White or Blue effect, not Red.
Burstflame Phoenix: Needs P/T
Goblin Dragonrider: If it rides Dragons, how does it give flying if it targets another Goblin, for example?
Silent strike -- like first strike, except for attackers only? Eh. Might as well make it just plain first strike. Its like "can tap but can't attack when it comes into play" recent thread.
Primal superiority -- creatures cannot attach to a creature. If it does, it automatically falls off. If you want to attach to a creature, you have to turn into an enchantment first. Even wizards has problems with this, hence the entire licids thing.
You have slews of cards dedicated to a mechanic that cannot work. Even if it did, you have cards that are extremely parasitic and will not work in any other set. Its worse than splice into arcane. At least splice and arcane spells can be used as standalone, if weak. You have spells that have unattaching attached creatures as a cost.
Insurgency -- fine on the surface.
However, you have cards which rely completely on insurgency counters. This means these cards are useless outside the set.
As for the cards themselves,
all the planewalkers need loyalty costs
some of the cards are wildly out of color; some of the black cards, for instance, have abilities that are green, white, and red, the only reason I can see them being black is because they're "vampires"
some cards are bork beyond imagining, like that 3cc indestructible artifact that copies ALL of the opponent's lands with a single activation.
some cards punish basic lands (such as fallout, which destroys all basics). This won't fly.
Yes, I realize some cards are completely borked out of their mind, but I appreciate the input
silent strike: Creatures that block this creature without first strike don’t deal combat damage. the compiler I used for the spoiler didnt realize that mythics are mythics, so it just put it at commons. It should be pretty obvious though.
Primal Superiority: Cost, T: Attach this creature to another target creature you control. Attached creatures cannot attack or block. If the creature that this creature is attached to leaves the battlefield, unattach this creature. Use this ability only as a sorcery.
Insurgency: At the beginning of your upkeep, if this creature did not attack or block since your last turn, including that turn, put a insurgency counter on this creature. Do not count turns in which this creature had summoning sickness.
THe file is attached.
Silent Strike: There are only 2 creatures with first strike in the entire set to counteract Silent Strike.
Command the Beasts: Name sounds Green, and the rules text is ambiguous. Did you mean 'creatures with objects attached to them'?
Swarm of Locusts: This card is pretty terrible. It involves jumping through hoops to get a bunch of 1/1 tokens that won't last more than 1 or 2 turns.
Vampire Beastvendor: You need to add a 'reveal' clause because the card searched for has a specific quality. Feels like a green card mechanically.
Garruk, Wielder of the Seal: Ultimate doesn't feel Green at all - land destruction on that scale is normally reserved for Red.
Seal of Duermis: This is a 3 cc artifact that would typically ramp up your mana by 3-4 depending on when you used it. This may be problematic.
Confinement Ring: See Faith's Fetters for the appropriate wording. Feels more like a White card.
Mind Annihilation: Almost always worse than Dissipate. Also, counterspells that don't actually say 'counter' on them tend to lead to arms races.
Aquamiran Seer: You will always be able to draw 2 cards of this on each of your turns because of the way priority works in Magic.
Fallout: Terrible card. Specifically hosing basic lands is poor design, and mass land destruction is either White or Red. Card name sounds like it belongs in either of those colours as well, not Black.
Silverblade Striker: A bit complex for a common.
Savage Vampire: Undercosted. The Titans are not a benchmark to cost creatures by. Even Green doesn't have a non-Titan creature that matches this in efficiency.
Hoarding Researcher: You're never going to attack with it (0 power) or use its ability after it blocks (1 toughness) anyway, so why not just automatically put a counter on it each of your upkeeps?
Master Revoker: Should just say 'Shuffle target creature into its owner's library'. This effect also effectively destroys the targeted creature, and isn't really Blue.
Stockpiler Jones: Way overcosted. 6 mana buys you 4 cards from Mind Spring. This creature needs to survive and takes 4 turns to do the same thing.
Lunar Melody: The randomness of the effect makes it feel Red. Undo is a much cleaner effect, but maybe bounce is supposed to be weaker in this set?
Time Legacy: This really shouldn't be a common. Rare caliber.
Shelira of the West Winds: 'tap up to'
Guardian of Aquamira: You need to define X.
Moondust Drake: 3U to cast 2 sorceries or instants for free is broken. Even getting a single Cruel Ultimatum off this would be crippling for your opponent.
Lightning Blast: Name is already taken: Lightning Blast, and X needs to be defined.
Valdarenan, Heart of Magma: Card should not be a common.
Fireblade Assassin: Not Red at all. Mechanically Black.
Turn to Cinder: White or Blue effect, not Red.
Burstflame Phoenix: Needs P/T
Goblin Dragonrider: If it rides Dragons, how does it give flying if it targets another Goblin, for example?
Furyblade: This is Black, not Red.
Extirpation: Better than Path to Exile.
Backstab your Allies: Why would White do this? Even the name sounds like something Black would do.
Angelic Visions: Reveal clause required, and card effect is typically Black.
Recollect the Past: Name sounds like it would involve retrieving something from the graveyard, and the card effect is Blue.
Soul Collector: Name is taken.
Parch the Earth: Card effect is Red, as is the name.
Walk the Trodden Path: Retribution mechanic feels White, not Green.
Gambit of Survival: Randomness and coin-flipping are Red.
Borgallian Rider: Game cannot track the value of X over turns.
Sphinx of Old Ages: When is this supposed to trigger?
Primal superiority -- creatures cannot attach to a creature. If it does, it automatically falls off. If you want to attach to a creature, you have to turn into an enchantment first. Even wizards has problems with this, hence the entire licids thing.
You have slews of cards dedicated to a mechanic that cannot work. Even if it did, you have cards that are extremely parasitic and will not work in any other set. Its worse than splice into arcane. At least splice and arcane spells can be used as standalone, if weak. You have spells that have unattaching attached creatures as a cost.
Insurgency -- fine on the surface.
However, you have cards which rely completely on insurgency counters. This means these cards are useless outside the set.
As for the cards themselves,
all the planewalkers need loyalty costs
some of the cards are wildly out of color; some of the black cards, for instance, have abilities that are green, white, and red, the only reason I can see them being black is because they're "vampires"
some cards are bork beyond imagining, like that 3cc indestructible artifact that copies ALL of the opponent's lands with a single activation.
some cards punish basic lands (such as fallout, which destroys all basics). This won't fly.
"Sometimes, the situation is outracing a threat, sometimes it's ignoring it, and sometimes it involves sideboarding in 4x Hope//Pray." --Doug Linn