MTG Salvation

There's also Felwar Stone to Exotic Orchard and Prismatic Lens to Shimmering Grotto. So I think it's a value comparison that stands.

Guardian Idol to Mutavault are close, as are Mind Stone and Horizon Canopy and Star Compass and Reflecting Pool.

Highland Fields
Land {R}
When ~ enters the battlefield, put a land you control on top of its owner's library.
~ enters the battlefield tapped.
T: Add RW to your mana pool.

Minister of Prahv 2(W/U)(W/U)
Creature - Human Advisor
T: Tap target land, then gain control of target red permanent, or return target nonland, nonlegendary permanent

(you guys post the silliest cards! This is not that hard, really)

Tome of Azorious 4
Artifact {U}
2W, T: Tap target creature.
2U, T: Draw a card.

I think this is probably balanced but I don't really like it; first of all, it's clunky and feels awkward to potentially get nothing from casting this. Secondly, almost all people will name zero and draw all lands they see, which is a very green effect by nature. Overall it's about as exciting to me as Covenant of Minds was, which is to say "not much".

Quote from Shukkets

In case nobody noticed, each of the wedge shards I've developed has a minor tribal theme. For black the tribe is Fungus.

Ok, but based on the way its worded here it merely means that this creature can't kill Funguses which is fine but seems unnecessary and also makes the card much more powerful in multiples for no apparent reason. Is there any reason this couldn't be:

Fungus Caller 1B
Creature - Human Shaman
B, T: Put a spore or -1/-1 counter on target creature.
Ferment 1B
1/1

Most of these I like quite a bit, although the charm shouldn't allow you to hit players since black generally doesn't do that so much through damage but with life loss (Douse in Gloom). In particular I like Birth, Sangovine, and Priests of Dinac. Fungus Caller seems weird - why isn't it just using -1/-1 counters?

I'll be honest - I'm not a huge fan of any of these. The examples here are mostly too complex, too weak/strong, or don't really fit the color pie so well. To use twobrid, I think you have to come up with something that green naturally does but that artifacts get too. For example:

NAME (2/G)(2/G)
Artifact - Equipment {U}
Equipped creature gets +2/+2 and has trample.
Equip (2/G)

This is a fairly powerful card at 2 mana for equip 1 and might push you into green, but it's pretty reasonable in limited at 4 mana for equip 2. Since this is Cube you could give it a splashy effect when it hits a player.

For the blue equipment:

NAME (2/U)(2/U)(2/U)
Artifact - Equipment {R}
Equipped creature gets +1/+1 and has hexproof.
When equipped creature dies, you may draw a card.
Equip (2/U)

Look, I took Skullclamp and gave it to blue and made the artifact version really expensive! Alternatively, you could make an equipment that turns a creature into a famous blue creature like Morphling.

Even when Wizards prints accelerators at 2 mana (Mind Stone, Pristine Talisman, Sphere of the Suns, Coldsteel Heart, etc.), they get heavily played in control decks and even in Cube. Llanowar Elves is a powerful card only balanced because it's a creature, dies really easily, has a color requirement, and can't be used the first turn. The only ways to make it fair are to make it take long enough to get out to basically equal suspending a mana rock (almost like Search for Tomorrow did).

Echo Mox 0
Artifact {R}
Echo 1
~ ETB tapped.
T: Add 1 to your mana pool.

You could do a Llanowar Elves-style card but I'm pretty sure this is still broken (unless you add Legendary but that's a reach I think).

Moxling 0
Artifact Creature - Mox {R}
~ can't attack or block.
T: Add 1 to your mana pool.
0/1

This version might need an ETB tapped clause.

Charge Mox 0
Artifact {R}
X, T: Put X charge counters on ~.
T, Remove a charge counter: Add 1 to your mana pool.

Lastly, this is probably not too broken, but it's not quite a mox.

Green Mox G
Artifact {U}
~ ETB tapped.
T: Add G to your mana pool.

The point is, Moxen typically give fast mana to any color, and red/green are really the only ones that deserve it. As Magic's history has shown, it's relatively trivial to win on turn 4-5 given a large enough card pool, so restricting fast mana to red and green at least limits the capabilities of combining fast mana with combo and control and thereby creating a very dominant deck. Think about it, there were not enough good artifacts in standard for a control or combo deck to run Mox Opal.

Corpse Replicant 4
Artifact Creature - Zombie Construct {R}
Whenever a creature is put into a graveyard, you may have ~ become a copy of that creature with this ability.
2/4

Nath'd

Dreaded Capsule 2
Artifact {M}
When ~ is put into a graveyard from the battlefield, destroy all permanents.

Kinetic Slime 1RG
Creature -Ooze {R}
Trample
Whenever ~ becomes tapped or untapped, it gets +2/+2 until end of turn.
1/1

(can get up to 5/5 but not on the first attack)

Ivory Hawk 4WU
Creature - Bird {R}
Flying, flash
When ~ enters the battlefield, return all attacking creatures to their owner's hand.
2/4

Inferiority of Birth 0
Instant
Inferiority Of Birth costs more to cycle for each card

Courage of the Conclave GW
Instant {C}
Target creature and all creatures you control with the same name get +0/+2 and gain lifelink until end of turn.

Haunted Kaleidoscope 3RW
Artifact
Whenever Haunted Kaleidoscope becomes tapped, put two 3/3 white Horror creature tokens onto the battlefield.
Whenever Haunted Kaleidoscope becomes untapped,