Wow!
Foldspace Rift. I love this Arcane teleport wall. Having it usable by either player follows the rule of every wall that it can be a double edged sword. The fact it does nothing without a second wall in play justifies its low cost. I would make it "Does Not Block LOS" (unclear) as then it has no function as a LOS blocker (a Fog Bank needs its purpose). As it is discretionary, I see it has no Passage Attack symbol. My only quibble is the Dune / Star Trek name reference: I think thematically as a fantasy game you would need to call it something like "Teleportal" or "Mordok's Portal" to make it more world-specific.
Reanimate Flesh. This is a lovely idea but it seems too cheap. For less mana than Heal's 8 dice, I know I can heal exactly 9 damage from my Elite or myself. Although the 0-0 range hurts. I like how the specific order means you can't use it at less than 4 life. I think a variant spell which uses your concept of giving Dark direct heal but at a steep price would be "Temporary Revival. Cost X mana where X = total damage on target. Heal all damage on target, replace with X/3 (round up) Rot markers" and also change target to a Living non-Mage Creature. This would make it an interesting two-way spell (like Negate) that forces you to heal any target non-Mage creature to full health but infects them with Rot instead. This follows the Warlock's "killing you slowly and painfully" style. For your spell, maybe reduce it to 9 healing, Dark 2 and remove the "Friendly"?
Akiro's Battle Manual. This is just awesome. The name, the card parameters, everything. I hope the designers like this and will send you something to use this idea. A shame it is not synergetic with Horn but maybe because Battle Orders is so weak, we give up on Horn for a future variant Warlord. I love this card, being able to get those double action flip flops is great. Like Mordok's Tome, this adds such a clever unquantifiable extra benefit.
What great ideas. Post the rest here?