This shows outstanding creativity, ACG. Here's my feedback on the rest.
Dreamcatcher. Nice title and idea but I don't think it will see competitive play, even with Lotus. Problem is Sleep is psychic so situational, Idol of Pestilence hurts Sleep etc. Situational augmenting benefits are always suspect as they are "win more". If you have Sleep on so many enemies, you don't need the extra Channelling. It may be useful in some niche match-ups where both players use Sleep effects. Also, what is the Dreamcatcher? Why is it flammable? Keeping to the card title, the Forcemaster really needs extra creature actions to time her attacks so I think this card will be very useful if it said "Zone Exclusive. Unique. You control all opponent's creatures with Sleep markers instead of that opponent". I appreciate Nightmare below is "in the same set" but +X Channelling is a bit vanilla in comparison.
Phase Barrier. I'm having trouble visualising what this Burnproof Acid Immune Force barrier is. Preventing damage out-of-turn during Damage and Effects step breaks the structure of the game (not even enchantments can do this). I also think you could create something more unique than a simple physical Force Wall by making it an Illusion. "Phantasmal Veil: Illusion Wall. Mind 1. Cost 4. No Access. No LOS. Extendable. Incorporeal. 1 Life. Once per round, before a friendly Action phase, Phantasmal Veil may lose its No Access and No LOS traits until the end of that round. Flip its Ready marker to Used to indicate this use." This retains your one-way accessibility concept whilst retaining the game adherence (so far) that walls apply to all players (here you only control when you open the wall to everyone).
I have considered a hard counter enchantment: "Counter Spell, Arcane 1, cost 2+X, reveal to counter attack spell or incantation of printed cost X targeting only this object". I also considered the hypothetical Endow keyword: "Pay 2 mana once before Damage and Effects to gain either 1 extra die or +2 on the effect die for that attack". Or alternatively the Stalwart keyword: "Pay 2 mana once before Avoid Attacks to gain either +2 armour or +2 on your defence roll for that attack". These are all uses of mana as temporary buffs or as a straight counter (with a 2 mana premium). The problem with phase barrier's mechanic is that it pumps life upon seeing an opponent's dice roll. There's currently no window for this, even enchantments can only be triggered between attack steps, not during. I also suspect the designers do not want to turn the game into an economic efficiency-based Eurogame where mana is the bidding currency for temporary benefits.
Green Slime. Nice idea of a self-replicating weenie! I think it's bit too weak a threat. For those stats, I'd add Flame +2 (traditionally use fire vs. Green Slime), Poison Attack (only affects living), Rot 11+ Devour (it turned you into Green Slime) and text: "Can only cast Green Slime spells. Cantrip while no other Green Slime is in its zone. Gain +1 attack for each adjacent zone with a friendly Green Slime. If Green Slime Devours a creature, it gains a Growth token" (Innate Life trumps Nonliving Finite Life). You differentiate it from Jelly (Jelly is acidic, Slime is more limited poison), encourage it to spread out across the arena and it can be vicious (6 dice Rot 7+ if victim is teleported into the centre of a 5 zone cross of 5 Slime). This may seem powerful but is so slow to set up and as Slow Full Action Attack, they are a specialist threat. This is why Jelly is so good as its utility is crippled by Slow Nonliving Full Action Attack.
Nightmare. Another really nice idea but I think this is too powerful as is. Firstly it needs Nonliving and all Incorporeal creatures so far have Upkeep +1. I also don't think it needs its "does not wake target" text. Attack on Sleeper is 3 dice critical with Sleep 7+ so has 50% chance of waking target (far more exciting). I'd add text "Mages suffer Daze instead of Sleep". Fast Flying makes it too much a creature assassin so I'd lose both, instead add text "when activated, pay 1 to teleport to any zone with a Sleep marker" as it interacts with any mage's Sleep effects. I like hybrid schools. I often feel mage books build themselves because spells are mainly in 1 school, like playing mono-colour in Magic, except you have to splash for essentials. However hybrid makes a card more expensive usually (Lord of Fire fits Warlock training perfectly). I always felt Bridge Trolls should have been just Nature 1 War 1 to be more played. So after nerfing the card above, I'd probably reduce it to Mind 1 Dark 1 (so costs Mind or Dark mages 3 points, rest 4 points).
I always wished the Forcemaster had this level 1 Mind creature: "Mind Worm: pest, psychic quick action melee attack 0 dice no damage unavoidable Taint 4+". This has your same idea of feeding on Sleeping victims without waking them while also potentially useful against other living creatures including mages,
Shadow. Yet another clever idea, using the Guard marker as a Banish 1 round (an Invisible guard cannot guard) to pump a Fast Elusive strike. It's like the "every other turn" more powerful attack of monster strikers in D&D 4E. I've only a few minor quibbles. It needs Nonliving, all Incorporeal creatures so far have Upkeep +1, the D&D Shadow sapped strength so Weak 9+ makes sense, Devour as D&D Shadows permanently killed victims and Light +2 extra vulnerability. I would consider the extra text "when Shadow devours a living creature, you may pay mana = 9 minus the creature level devoured to summon another Shadow in its zone from your spellbook". This creates the "devour to multiply" mechanic in line with our D&D expectations. Shadow is a Spirit cousin of Gray Wraith, just more of a pouncing assassin.
Spatial Disjunction. Lovely idea, all smoke and mirrors, no damage, befitting an arcane trickster. However, it is far too powerful. No need to create a Blink keyword, just replace with Push (lower cost to 2+4 magebind 2). Explaining why Blink teleport 2 is too powerful is another subject altogether. Make it a random direction like Repulse. Call it a "Circle of Repulsion" or similar instead. I really love the flavour text!
Haunted. I like all the concepts behind it, the creature paying for that murder by being harassed by spirits with haste. Obviously it needs Spirit support (like Shadow, Nightmare etc). It can be used with friendly creatures to create a walking spawnpoint like the Tome (except a cantrip crucially) and Warlock can collect both it (cantrip) and another curse via curseweaving. No quibbles here, just needs Spirit support, perhaps for any future Witch.
Murkh's Belt. I've long advocated a similar upkeep enchantments mechanic to encourage the Warlord to use Commands, not persistent enchantments. This is a far better idea than my over-powerful Epic conjuration. I think you overpriced it, 6 cost and War 2 would be fine for an in-zone only effect. The Warlord needs all the help he can get.
Rally. Yet another improvement on a mechanic I proposed (mine was an Epic enchantment like Divine Intervention to teleport any creature to Warlord's side, adding a Guard marker on it). I like how LOS is not needed as this encourages Warlord to use earth walls. This is really powerful so must be a full action, not a QC. It's so powerful that I would add "No more than 1 creature from each zone" so as to encourage prior territory gain. Also, as an Epic spell, I would call it something more grandiose like "Summon the Horde!" Nice spell if nerfed slightly!
Magic Bottle. Nice idea (as always). However, creating this quick cast summon mechanic may "let the genie out of the bottle" so to speak. I am not comfortable with this as it could make future creatures with coming into play effects too powerful if summoned via a quick action. However, you are spending a quick action preparing it (or Battle Forge) so it is a combo prep for action burst mechanic, like Enchantment Transfusion. So maybe it would do the game good to have more combo enablers. Out of all your ideas, this has the greatest possibility for abuse. I'm comfortable with potions not using up an item slot (the "only one" rule prevents abuse). I'm not so comfortable that dissolving it after it has 3 mana can trigger its summon. I would nerf the text to "You may bind any non-Epic creature from a trained School to the Magic Bottle. When Magic Bottle has at least 3 mana on it, you may destroy it as a quick action to summon the bound creature in your zone." This means Dissolve effects (Orchid) can still destroy the Bottle without letting out the creature otherwise there is an unstoppable inevitability of it just like with Enchantment Transfusion and current "move to counter targeting" FAQ rule. I limited it to trained School creatures so that Air Wizard can have classic Whirling Spirit, Beastmaster can bind a Grizzly into it etc. This is the one card here that could be a great combo enabler but needs thorough testing and by limiting the quick action to in-school creatures, we are retaining the mage's theme and limiting possible future abuse.
Anyway, you asked for feedback. I hope you don't mind the minor criticisms as I've been mostly highly positive, and it's only one person's opinion. What's important is you impress the design team with your undoubted creativity and ability to translate fantasy tropes into game mechanics. I hope they take you on as a Playtester as you've got a flair for (a) great mechanics innovation and (b) theme, including flavour text. A perfect combination, ACG!
