Void Hamlet wrote:tristan_durst wrote:Outerplanes to Innerplane travel Is impossible without a trip through the Prime. There is no connections between Outer and Inner planes.
Are you sure? Even through the Infinite Staircase of Ysgard? (When I am not sure, I ask)

Two points on planar travel:
Just being on the Outer Planes doesn’t make getting around easy. There’s still vast distances to be covered and mystical barriers to be crossed. It helps for a fellow to know the ways and means of quickly getting from place to place, unless he wants to spend a lifetime just crossing from one portal to the next on the Great Road.
First, a cutter can always use the Astral Plane in pretty much the same way a prime uses it to reach the Outer Planes. Through spells or magical items, a blood can step into the Astral and then will himself to his destination. It takes power and practice, but it can be done. The astral method’s not perfect, though. The Astral only touches the uppermost layer of each plane on the Great Ring. If a fellow wants to go to Mount Celestia, for instance, he can only get to the first layer this way. He’s got to find another way to reach the seventh layer (or the second, for that matter).
Fortunately, other, more efficient means of getting around exist. There’s conduits, just like those that thread the Astral Plane (see page 21), which link different layers of a plane. These conduits can even link different layers of different planes. It’s said there’s a conduit on the 492nd layer of the Abyss that’ll carry a being to the first layer of Ysgard, which just might make for a handy escape someday. These conduits can be either young (one-way) or mature (two-way). Most conduits are pretty stable, and maps to many of them can be bought in Sigil. ’Course, fakes are available for purchase, too. The biggest problem with conduits is they don’t always take a body where he wants to go. Step through a conduit and a berk may still have long distances to travel.
Every plane’s got regular paths between the layers, too. On Baator, a sod can pass through the gates of the city of Dis and end up in the bog of Minauros, the next layer down. On Elysium, a body can sail down the River Oceanus to reach the next layer. To use these, a being’s just got to know the dark of them. They’re not as quick as conduits, but their dependability makes them regular trade routes. These roads are also used for formal occasions, like when one power goes calling on another. It’s the polite thing to do.
Finally, there’s Sigil’s portals. Just like the portals to the Prime Material and Inner Planes, Sigil’s got doorways to more places on the Outer Planes than can be mapped in a millennium. For most planars, or at least those that can get to Sigil, the portals are the preferred way to travel. Odds are good for finding a door at least somewhat close to where a cutter wants to go - if he’s willing to search the streets long enough.
And
Elementals summoned on the Outer Planes aren’t the same thing as those creatures that appear on the Inner Planes and the Prime Material. Since the Inner Planes are pretty well cut off from the Outer ones, spells that call upon an elemental creature actually create one from the elements of the plane where the spell is cast.
That means these monsters are going to act a bit differently from the real thing. First, the elemental adopts the alignment of the plane where it’s created. It’ll refuse to do anything that would contradict that alignment. This also means that elementals created on the Lower Planes have a little of the deviousness that other natives possess, so a spellcaster better watch out for tricks, misinterpreted instructions, and outright treachery. Finally, the chance for an elemental to break the caster’s control over it increases by 5% for every plane between the monster’s and the caster’s (as determined by faction plane of influence) - the system is the same as that for priests casting spells. Luckily for primes, that last problem doesn’t affect them.
About the World Tree
One magnificent feature of the planes is the great tree Yggdrasil, the World Ash. Rising on the first layer of Ysgard, Yggdrasil’s roots and branches extend into many other planes, providing yet another way for travelers to get around. No one has mapped the extent of these pathways, but some of the important paths are known. One of the roots reaches to Niflheim on the Gray Waste, and another stretches to Pandemonium, where Loki [of the Norse pantheon) resides. The branches are no less widespread, even crossing the silvery void of the Astral Plane to reach the very Prime Material. There, it’s said, the smallest branch tips touch hundreds of worlds where the Norse gods are revered or remembered. Other branches reach Elysium, the Beastlands, and Limbo, and there are likely to be many more
such pathways.
Traveling Yggdrasil’s paths requires the traveler to climb through the branches or roots. At each planar crossing, the tree disappears through a portal of shimmering color, like a color pool found on the Astral. Only the vaguest of shapes can be seen through the window. To know for certain what lies on the other side, a traveler must step through. The colored portals are all two-way passages.
All Information is from the DM’s Guide in the Main Boxset for Planescape.
So, seeing the only way to travel around the outer planes is through the Astral Plane, there is no connection to the inner planes. The outerplanes are connected to the prime via the Astral, while the Etheral plane is what connects the Inner planes to Prime materal plane. The Astral, and Etheral planes do not actually "touch," so Standing on Alfheim, and trying to go to the Plane of Water would be immpossible unless:
A. The planewalker cast a spell to send them to the prime via the astral, then cast a second spell to get to the plane of water, via the Etheral plane.
B. Uses a magical device to transport himself to the prime, and then to a Inner plane.
C. Goes to Sigil, the only place in the outer planes that does have connections to the inner planes, and uses a portal.
The City of Sigil is a rules breaker. The portals there can lead anywhere, included worlds with modren Technologies. IIRC there was an Adventure where the PCs went to a "junk" world where they found parts to the Space Shuttle, and a locomotive. Not sure which one it was. Also, Technology exist on some worlds, as ancient artifacts. Mystara's backstory, as told in the Immortal boxset, Before Galantri and Rockhome, a Spacecraft crashed landed on the planet, and the resulting Nuclear explosion tilted the world on its axis!!
-Tristan