After you complete the Snake's Remains dungeon, the Maku Tree tells you to go to Spool Swamp, which is to the west.
About Animal Companions
Please Note! In this game, you can befriend Ricky the kangaroo, Dimitri the Dodongo, or Moosh the bear. You can only befriend one of them, and the choice is permanent. If you don't get Dimitri or Moosh's flute before you go to Spool Swamp, you will lose the opportunity to befriend Dimitri and Moosh. If you want to befriend Dimitri the Dodongo, you have to win the Strange Flute from the Subrosia Dance Hall (it's random, so it could take a long time to get it), and you will also need at least 80 rupees. If you want to befriend Moosh the Bear, you have to buy the Strange Flute for 150 rupees from the Horon Village shop. If you don't get one of those flutes before you go to Spool Swamp, Ricky will become your animal companion for the rest of the game.
Go toward Spool Swamp
From the Snake's Remains entrance, go west, then north, and turn it into winter. Then go south until you reach some ice, and walk west over it. If you want to befriend Dimitri, and you don't want to befriend Moosh, then go west to the Subrosia portal, and play the Subrosia Dance Hall game until you win the Strange Flute (which becomes unavailable after you enter Spool Swamp or buy the Strange Flute from the Horon Village Shop), then go back through the portal and go east so you are in the screen with ice (or water) on the east side. Go south until you can't go farther south, then west, then south, then west. You should now be in Horon Village. If you want to befriend Moosh, and you don't want to befriend Dimitri, buy the Strange Flute now from the Horon Village Shop! It will disappear as soon as you enter Spool Swamp! If you already got the Strange Flute from the Subrosian Dance Hall, you can no longer purchase the Strange Flute from the Horon Village Shop.
Point of No Return!
Go north from Horon Village until you reach the screen with two rocks blocking the path north. As soon as you go north past where the rocks are, you will lose the chance to befriend Dimitri and Moosh if you didn't get one of their flutes! If you are ready, lift the rocks and go north to Spool Swamp.
There are Buzz Blobs in this area that will zap you with an electric shock if you hit them with your sword. You can kill them by throwing an Ember Seed on them.
Get Scent Seeds
North from the entrance to the swamp is a Scent Seed tree. Scent Seeds attract monsters. If you drop one, monsters will walk toward it.
Get Ricky's Gloves
You can optionally go west to find a kangaroo named Ricky. He would help you get to Spool Swamp but he lost his gloves to Blaino.
Go east from the Scent Seed tree (described in the previous section) and go south to find Blaino's Gym. Bet him 10 rupees to fight a boxing match against him. Press A and B to throw punches. (Even though you make the "ouch" sound when he hits you, you don't actually take damage.) Avoid his punches and try to hit him where he's not blocking his body with his gloves (i.e. after he throws a punch). When you push him out of the ring, he gives you Ricky's Gloves.
Be sure to re-equip your items, and your ring, before leaving. Go north then west from Blaino's Gym. Keep going westward, across a small bridge.
Optional: Plant a Gasha Seed
In the screen with the small bridge, go to the west side of the bridge and go north until you reach a screen with a tree trunk that you can crawl through. There are Darknuts in this screen. Defeat them, then use the shovel to dig near the middle of this screen until you find a patch of soft soil. You can plant a Gasha Seed there if you wish.
Find Ricky
Go back the way you came until you are in the screen with the small bridge. Go west, then north to reach Ricky. Talk to him to give him the gloves. If you didn't get one of the flutes mentioned above, he will give you Ricky's Flute, which lets you summon him no matter where you are. Either way, you automatically jump into his pouch.
To punch, press A. Hold the A button to charge up a tornado punch. Press B to get out of the pouch. Walk up to Ricky to get back into the pouch.
Enter the Swamp
Go south until you reach a screen with holes blocking the way. Ricky says that he can jump over gaps automatically, but not more than one hole at a time. Push toward the holes and he'll jump over. Continue south. Ricky doesn't get zapped by Buzz Blobs, so just punch them to get rid of them.
Along the way, you will pass by a house. Press B to jump out of the pouch. Ricky will wait for you outside. In the house, you find a woman who says that she feels too hot, and needs something creepy to send chills down her spine. If you have the Ghastly Doll, she will take it and give you an Iron Pot.
Outside, walk toward Ricky to jump back into the pouch. North of the woman's house you find a cliff. Ricky explains that he can jump up the cliff in one leap. Just push on the cliff and Ricky will jump onto it. Go north, then Ricky will go back home. The swamp is to the north.
You'll pass by a sign that says Tarm Ruins are to the north. You can't do anything at the ruins right now, so you can just ignore it and go west.
You'll find a Pegasus Seed tree. Hit the seeds with your sword to put them into your seed satchel. If you use a Pegasus Seed, you walk more quickly for a limited time.
As you make your way into the swamp, you'll see Sokra sleeping on a ledge that you can't reach. If you go north then east from him, you find a house where the guy says that he lost the key to the floodgates. There is a lever in the bottom-right corner of the house. Hit it with your sword to drain the pool in the house. The Floodgate Key is there. Take it. The old man says that you can reach the floodgates from the puddle outside. Go outside to discover that the water here has drained, too. Go down the stairs there.
The owl statue says to use Pegasus Seeds. Step on the switch, then use a Pegasus Seed and run across the bridge.
In the next room, push the rightmost green rock up, and the other green rock down. Use the Power Bracelet to pick up the brown rock, then push the bottommost green rock left and the one above you up. Go down the stairs.
Follow the path around this area and lift rocks to reach the stairs at the end. Keep going until you are outside again.
Go south. You can optionally go east and talk to Sokra. Continue south to find a Business Scrub who says that he saw a strange vortex south of the floodgates. He offers a shield for 50 rupees. You can get a cheaper one in Horon Village, so don't bother. There is hidden soft soil under the rock in the screen with the Business Scrub.
Go east from the Business Scrub and push the keyhole to use the floodgate key. This lowers the water down below. Go back to where you can see a tree stump down below, and go east from there, to where Sokra is sleeping. Jump down off of the ledge.
Go west. Jump onto the tree stump and use the Rod of Seasons to turn it to winter. From the tree stump, go east, then south until you are in the swamp.
Spool Swamp with Ricky
If you have Ricky, then just jump up the ledge on the left side of the screen. Make your way west, then south until you encounter another cliff. Go up it and go south. Use a tornado punch (hold A to charge up) to get rid of the bushes between the holes. Jump over them and go south. In the next screen, there is a hidden patch of soft soil under the rock. There are hidden Pincers in holes in the ground in this area, so be careful. If it's winter, keep going east (being careful of more hidden Pincer enemies) until you can't go east anymore. Dig through the snow and bomb the wall and go in. The chest contains the Square Jewel.
Go back outside. Make your way west, avoiding the hidden Pincer enemies. When you are in the southwest corner, lift the rock to find soft soil. Then go north, lift the rock, and use the Subrosia Portal. Skip to Rosa's Ribbon to continue.
Spool Swamp with Dimitri
If you got the Strange Flute from the Subrosia Dance Hall, then from the first screen of the Swamp, go south, then east, then north. You'll find Dimitri surrounded by Pig Warriors. Talk to the Pig Warriors and pay them 80 rupees to leave Dimitri alone. You can now hop onto Dimitri's back. Press B to get off of Dimitri. Press A to make him eat whatever is in front of him. He can eat almost any enemy. He can also eat bushes and piles of snow. He can swim, and can even go up waterfalls. You can also pick him up and throw him using the Power Bracelet.
With Dimitri, go south until you can't go south anymore. There are hidden Pincer enemies in holes in this area, so be careful. Dimitri can eat the Pincers as soon as they come out of the hole. If it's winter, dig through the snow on the right side of the screen and bomb the wall and go inside. In the chest, you find the Square Jewel.
Go back outside. If Dimitri is not there, just play the flute to summon him again. Make your way west. Remember that Dimitri can eat the Pincers as soon as they come out of the hole.
When you reach the southwest corner of this area, watch out for the Pincer, and go lift the rock in the corner to find a patch of soft soil. Then use the northeast exit. Lift the rock and use the Subrosia portal. Skip to Rosa's Ribbon to continue.
Spool Swamp with Moosh
If you got the Strange Flute from the Horon Village shop, then from the first screen of the swamp, go south, then use the southwest exit. Go north from there to find Moosh. He'll scare off some monsters who are harrassing him. Go up and talk to Moosh. The monsters come back, so get rid of them with your sword, then talk to Moosh again.
With Moosh, press A to float in the air. Keep tapping it to stay afloat, but keep in mind that you will slowly float back down. While hovering, hold the A button to charge a Ground Pound. To get off of Moosh, press B.
From where you found Moosh, go south, then east. Float over the holes, and continue south and float over those holes. From there, go east, then south. Be careful of the hidden Pincer monster in this screen.
If it's winter, dig through the snow and bomb the rock wall. Go inside and open the chest to get the Square Jewel. Go back outside. Make your way west, avoiding the hidden Pincer enemies. When you are in the southwest corner, lift the rock to find soft soil. Then go north, lift the rock, and use the Subrosia Portal.
Rosa's Ribbon
When you arrive, you're in a screen with a volcano, so get out of this screen. There is a beach to the south where you can find star-shaped ore in the sand. Just dig with your shovel. It's rare, so it might take a while.
Go north from the beach and go to the northwest part of this area to find the Subrosia Market. You can get a shield here (the seller thinks it's a cutting board) for 5 Ember Seeds. You can also get a Piece of Heart (the seller calls it a "rare peach stone") for 20 ore chunks and 10 ember seeds. And finally, you can get the ribbon for star-shaped ore. If you don't have star-shaped ore, go south to the beach and dig in the sand with the shovel until you find it. Then get the ribbon.
Go outside and go back into the market. You can now get a ring for 30 ore chunks, and big bomb bag (it lets you carry more bombs) for 10 bombs and 50 ore chunks.
There will be another ring in the market after you buy the first, and there will be a Gasha seed where the bomb bag was. When you buy a ring, go outside and go back in and there will be a new ring in stock. After you buy a ring for 70 ore chunks, the seller will have ember seeds there instead.
A Date with Rosa
Now that you have the Ribbon, go back to Rosa in the southeastern corner of the beach and give it to her. She'll go on a date with you and ask you to take her to the temple. With Rosa, go north from the market. Push on the locked door and it will unlock with Rosa's key. Go to the west side of the indoor area and unlock the door, then when you are outside, go east to reach the temple.
In the temple, go to the northwest and unlock the door. Inside, lift rocks so that you walk up the middle of the room. Lift the rocks and go up the stairs. Keep going up to reach the altar. The spirit will add the power of Summer to the Rod of Seasons. She tells you to remember that in the summer, vines grow and creeks dry up.
Take Rosa back to the spot on the beach where you found her and she'll thank you for the date.
To the Next Dungeon
If you don't have a shield, be sure to get one before you continue on. You'll need it in the next dungeon. The Subrosia market has one that you can get for ember seeds, and the Horon Village shop has one for 30 rupees.
You need to go back to Spool Swamp now, so go use the portal next to the volcano where you first arrived in Subrosia from Spool Swamp.
Lift the rock and go south. Make your way to where you used the floodgate key to the north. Go north from the keyhole, then west to find a tree stump. Use the Rod of Seasons on it to turn it into summer, then go north. Use the vines to climb into the entrance to Poison Moth's Lair.