Land Designs

{Judging!}
Akai Ryu
Redsun Grove: You really threw balance out the window for this one. Even with Tolarian Academy it is theoretically possible that you don't have any artifacts and thus can't get any mana, but this card is a plains/forest, meaning it has inherent tap for or . Which already is OP on its own. For making decks it forces the player to use (perhaps nonbasic) forests and plains, which is an interesting need.

kefke
The Shadow Academy: I am not very familiar with Phasing gameplay wise, but from what I've seen, it's mostly meant as a downside for strong cards that let you have a card on the field half of your turns. Having phasing on the land itself is a nice downside. Having a land have a downside be a big upside with mana of any color as well is not necessarily too great, but having it be tied to something that only happens half of the time is better. It's very hard to judge this card for me.

gamma3
Growing Cityscape: This card would be horrendously powerful in mono-colored decks, where you can play basic lands to your heart's content. Its downside isn't that harsh for what it does either and the effect isn't necessarily that interesting. Bonuspoints for basic-land love. Also having this be an uncommon is a no-no

qorbin
Hall of Goblins: I like that the land gives you only if you have goblins (which also is an appropiate colour), meaning that you could not get any mana at all. Nontoken is also an important design element. I however do not agree with Goblins being the race that this land creates mana for, as Goblins are known for how easy and how many of them can be played. A more costly race I would agree more with. Funwise it would make Goblin decks even more rushdown as a one mana goblin creature essentially pays for itself when this land isn't tapped yet. Games would be done one two three.

viriss
Leyline Nexus: I like how this promotes having multiple basic land-types, which narrows use of lands in a deck. It rewards using multiple colors in a deck, which isn't a good thing in my opinion. It does give only colorless mana though, which isn't as useful for a multi-color deck. It's a funny balance there. Bonuspoints for basic-land love.

augur
The Last Haven: I like that you need to tap for before you can use the main ability. It makes it only becomes useful when you already have a few creatures on the field, making a win more card. It might get out of hand quite quickly with token-centered decks though.

Jartis
Storm Tower: Looks pretty fun in that you can keep laying it on people even after Preordaining, but it's horrendously powerful when combined with, well, storm. And cascade. Outside of those abilities, it looks like a milder ability (relatively speaking of course, still very powerfull).

xylophone
Assembly Plant: I quite like this. Allowing for the cycling is a smart design move, and means you won't have a dead card in hand while still being able to have the land be high risk/high reward once on the field. and a tap is a pretty hefty price, but there are ways around that. Like clones, using Mishra's Factory's creature ability (which makes it more viable as well), and doubled token generation. But this means you're also building a deck with this card in mind, making those decks just a little bit stronger (but not necessarily by much as it's but a very destroyable bear that's being copied/cloned/etc). I like it.

Daij_Djan
The Cathedral of Galithen: I really like the flavor of this card, clerics praying to get angels and gods to come to the battlefield essentially. The cost of and tap seems pretty fair as this card can only be used in decks that contain both clerics and gods/angels. And the decks that have both of those are pretty casual and not viable. Which might not be the case anymore with this card (though it being legendary makes the impact that this card can have less hefty). Anyways, nice limits for the adding of mana that are also flavorfull.

HvT
Ancient Petraglyphs: As instants and sorceries are very quickly put into the graveyard, I think the and tap isn't enough of a setback, especially in spells-only decks. Good that it enters tapped though. Flavor is nice.

{Winners!}Third place goes to: viriss with Leyline Nexus
Second place goes to: Daij_Djan with The Cathedral of Galithen
And the winner is: xylophone with Assembly Plant!

{Rambling}This was actually a really cool challenge to do. I've been playing around with the idea of having lands with the "rift" subtype to go with an idea I came up with of a plane running out of resources and tapping into other worlds to fill their needs. I couldn't really justify the use of a subtype though. Especially not for something equivalent to a basic land, which I wanted to represent. In designing for this challenge, I started really looking at what a new subtype would need. The obvious answer was there need to be cards that care about the subtype, and to show that off, it would have to be the lands themselves. I also wanted to avoid the "Locus Problem" of having lands that care about specific things in play spiralling out of control. So, I came to the thought "What if rifts were like the land version of slivers?", and worked from there, deciding that to balance out having a lot of abilities the rifts would all ETB tapped, each ability had to have a cost, and that cost would always involve tapping. As a bonus, here's a couple other ideas I worked out, aside from the main submission.

{viriss}Nice Dragon and artifact tribal. I like those mixed themes. Has a real lair feeling to it.

{kinotherapy}A Flavourful desert. I think the activation should cost , , Sac; since it is quite a good enabler for decks that just want to fill their graveyard.

{Jartis}This is definitely way too powerful. Even if it also effects your opponent's creatures. Maybe make it an activated ability or let it trigger off something like a gree-blue creature entering. Drawing cards would also be insanely powerful.

{kefke}"Sliver--lands" is a neat idea. i like all three of them. Lands without mana abilities are somehow weird, but I guess in the right environment it's ok.

{melono}I like them getting better the more you play. (I guess i'm into parasitic designs.) Having only the first one enter tapped is also interesting, although I don't know if its too strong. If it was, maybe consider somehting like a negative fastland and check for more other Shelters.
The red one seems to be the most underwhelming of them. (To be fair, there are not many things that do this. Still it's kind of restrictive and only makes sense if you play against blue.)
Preventing attacks is kind of weird in (modern) blue. Maybe it taps unless they pay ?

{ominividrus}This is pretty powerful. Maybe a bit too powerful, maybe not.
I don't really see hwo a chamber is a gate?
As xylophone mentioned, that wording doesn't work. The trigger will be put on the stack after your upkeep (in the untap step nothing can be put on the stack) so the Chamber will already be untapped. You need something like the woring of Rasputin Dreamweaver for this: "At the beginning of your upkeep, if ~ started the turn untapped, ..."

{monger}interesting locus. I was wondering why it didn't sac on activation, then I reallized that it wouldn't count itself.

{HvT}Fun land. Kind of funny to have a card that produces energy wihtout using it. I'm not sure if this is ok or busted to just produce energy "for free".

{OLD1}