The elves of the Holy Corellon Federation understand ecology very well. This is partly due to a desire to protect nature from civilization, but mainly due to a desire to protect civilization from nature. Under certain conditions, magical creatures can grow powerful enough to destroy entire cities, and can only be stopped by a high-level adventuring party or a major military power. Knowing what conditions cause these creatures to grow, and to leave their natural habitat and move into settled lands, is a vital skill for any government.
The more chemical and magical nutrients a biome has, the more life it can support. In general, when a biome supports more life, its food web is more complicated, its apex predators are more powerful, and it is more likely to have herbivores that are capable of fighting those predators.
In space, biomes are isolated. While some things do migrate through empty space, food webs are generally contained to a single archipelago. This means that a trained surveyor with the proper equipment can quickly scan a group of sky islands and estimate how rich its ecosystem is, and therefore how powerful the creatures in it will be. The wildspace navigation charts used by League members, purchased from the Federation elves who originally charted the region of space, have this information.
On the morning of the crew's fifth day of sailing, Mabellyne approached Ra fal with a sheaf of navigation charts. "Is this a good time to talk?"
"When I started my shift this morning, I double-checked the navigation charts for our approach to Garcia-17, and noticed that it is listed as a Level 3 biome."
Ra fal glanced over at Mary, who was practicing tying knots and looking at some clouds in the distance. The human did not appear to be listening to them, but Ra fal guessed that she probably was. "And it would probably be best for everyone if we did a Level 1 island first."
"Unfortunately, none of the Level 1 turnip islands are close by. There is a nearby Level 1 archipelago with both gravity islands and zero-gravity asteroids for us to practice in."
"How much would that delay us?"
"Only a couple hours for the course change and docking, if we make the course correction now. Plus however much time we spend training."
"It is worth spending an extra day on this." Ra fal grinned. "It will be good for us to kill a lot of bugs together."
"Should we wake Sofonisba and Gladys and have a crew meeting to discuss this before we commit to changing the plan?"
"Yes. They will almost certainly approve, but we should always be in the habit of doing things based on consensus."
Everyone quickly agreed to the plan. Sofonisba had not entered her meditation trance yet and was fine with talking. Gladys gave explicit permission for the crew finalize future decisions without her input if at least four people agreed, with the obvious implication that she cared more about her sleep than the feeling of being consulted, and went back to bed. Mabellyne and Tsinta made the course correction.
Later that day, after the shared meal, when Mary and Ra fal would normally be sleeping, they approached the island to dock. By unspoken agreement, Mary and Sofonisba were on their broomsticks again, moving alongside the ship as the rest of the crew prepared for their first island docking. Also by unspoken agreement, Sofonisba explained what was going on.
"In order to dock, you need to know exactly where the island's gravity plane is, and how far out the gravity bubble extends. They are going to toss a gravity probe soon."
The ship was moving very slowly under propeller power, with the sails furled and the wings in steering position. When it was a few hundred feet away from the island, they saw Gladys toss a disk toward the island. It spun slowly through space in a straight line, flinging off a cloud of glittery flakes that expanded in a cone.
When the probe was about 150 feet from the island, its trajectory suddenly changed into the familiar parabola of a stone thrown in gravity. It hurtled down for about a second, but then, when it went under the ground level of the island, its motion changed again. It slowed down, and then started rising back up to the ground level just as fast as it had fallen. When it passed the line, it started falling again. It repeated this cycle, bobbing up and down three times before hitting the rocky side of the island.
"Why does it do that? I thought it would just keep falling down?"
"A gravity plane actually attracts things from both directions. It extends a lot further out in the Air direction, but right at the plane, when a thing passes through, gravity reverses for it and it falls back."
"Yes. You can use it to your advantage, sometimes, if you can get accustomed to what the gravity changes do to your stomach. We may get a chance to practice later."
The flakes it had been spinning off followed its motion, falling and bobbing with it. Soon they had settled down, slowed by the air, and were drifting on the gravity plane and making it look like a rippling water surface. The flakes further from the island, however, simply stayed in space without moving, making it obvious where the island's gravity started taking effect.
"Now they need to line up the ship's center of mass as close to the gravity plane as possible, so that the ship does not bob up and down too much when it enters the bubble."
Mary and Sofonisba watched as the crew carefully inched the ship forward and lined it up with the island's gravity plane, using the wings to make small corrections up and down. Mary held her breath as the bow of the ship came within a few feet of the gravity bubble, even though the painted center-of-mass line on the ship's hull was almost exactly lined up with the glittering flakes. Closer, closer...
And then a sudden gust of wind pushed the ship forward and down.
At any other time, this would have been insignificant, a deviation of a few feet easily fixed by shifting a wing. But the elemental keel was turned off for the approach, and before anyone could react, the bow of the ship was inside the island's gravity bubble and under the plane.
The bow lurched up, while the stern kept moving down on its previous trajectory. Soon, all of Fortuna's Kiss was inside the gravity bubble, bobbing around like a ship on a stormy ocean, and moving towards a collision with the side of the island.
Mary screamed, "What do we do?"
"Catch anyone who falls overboard. Go between ship and rocks. You take starboard."
Mary nodded at Sofonisba's calm command as the elf rapidly moved to the ship's port side. She moved her broomstick forward a bit, and closer to the ship, looking at her friends to see who might be in danger of getting thrown off.
Gladys, Ra fal, and Tsinta were fighting with the wings and sail and accomplishing little, but Mabellyne quickly shifted the engine into reverse and activated the overdrive. The propeller spun rapidly, quickly stopping the ship's forward momentum and saving it from any collision.
However, the sudden change in the ship's velocity happened at the same time that the ship was under the gravity plane, meaning that it and everyone on it were falling up. Ra fal, able sailor that she was, had a firm experienced grip on the railings and rigging that would be dislodged by almost nothing. Mabellyne was prepared for the velocity change and holding on, but both Gladys and Tsinta flew forward over the ship's railing as it reversed.
Gladys was flying starboard toward Sofonisba, and Tsinta was going directly forward. Mary flew her broom forward as fast as it could go to catch Tsinta, but misjudged the velocity and overshot. She then wheeled around, putting herself between Tsinta and the island, and then used her foot to stop the velocity of the slowly spinning elf, just like she did when bouncing off asteroids. Then Tsinta was able to grab her waist and get on the broomstick behind her.
"Where should I take you?"
"Back to the ship."
Mary moved the broomstick forward, but was surprised at how much harder it was. It was like she was carrying the elf while running. She could feel fatigue build up by the second. But it only took a few seconds to get back over the still-bobbing ship. Tsinta leaped gracefully off the broomstick, but ended up landing badly and sprawling on the deck as the ship heaved unexpectedly.
Mary looked over to check on Gladys, and saw that Sofonisba had already landed her on the island.
The ship's bobbing was less violent now. Mary saw the wings catch the air and slow the ship down a little with each motion. As soon as Gladys found a firm footing, Ra fal threw a line to her. The line missed, but Sofonisba quickly flew out to grab it where it had fallen into the gravity plane and handed it to the goblin. Gladys carefully hauled on the lines to control the bobbing, heaving and tugging with her great strength. As she was doing this, Ra fal and Tsinta used the wings to get the ship back under control, and soon the three of them were able to bring the ship in close to the island.
Tsinta tossed another line to Mary and gestured to her to tie it to a rock. Ra fal threw another to Sofonisba, and soon the ship was securely berthed.
They found Mabellyne curled up in a ball near the engine, nauseated and barely able to move. She had been violently ill, but had managed to catch everything in a waxed paper bag.
Gladys gave Mabellyne water and a pill, which seemed to help, and then Ra fal held her hand.
"You did good. You saved the ship from crashing by reversing the engine."
Mabellyne nodded weakly.
"Do you want me to get you to land?"
Mabellyne nodded again. Ra fal easily and tenderly picked her up and carried her over the gangplank to the island.
"Most people get spacesick the first time they bounce around on a gravity plane. The lurching up and down and gravity changing direction even started to affect me, and I have been sailing rough waters for years. You kept yourself together really well. Did you have that bag on you the while time?"
Ra fal deposited Mabellyne on the green grass and soft loam, but only after making sure that Gladys, Tsinta, and Sofonisba had formed a perimeter to keep watch for any danger. She raised her voice to address everyone.
"Well, that could have gone a lot better. But we are all in one piece, the ship is fine, and we got some good experience. You all did good, really good. Now we can prepare for the hunt."