The Legend of Zelda: Oracle of Seasons/Eyeglass Lake and Unicorn's Cave

Before the next quest
Two important items were obtained in the previous chapter: the Zora flippers and the power of spring.

Using the flippers, Link can explore the river between North Horon and Holodrum Plains. Starting from the north, Link can find an islet with a L-3 Gasha spot, then a cave with a man waiting for five Essences (come back later). Continue swimming west, and explore a cave with a magic ring chest inside, then Link will reach Spool Swamp.

Using the power of Spring, Link can get a Heart Piece in the Spool Swamp.

Also, Link can progress along the trading sequence. Bring the mushroom found on the mountains to Syrup the Witch in Sunken City: she excanges it for a wooden bird. This item is needed by the clockmaker in Horon village, and he trades it for some lubrificating oil. Link can then bring the oil to the musician in the eastern suburbs and trade it for a phonograph. This is the second-to-last item in the trading sequence, that will be completed during the next chapter.

Eyeglass lake
This region is just east from Impa's hideout. The default season is winter, and during this season there is only one notable feature: a L-4 Gasha spot. Plant a seed there.

Nothing special happens during springtime. In summertime, instead, the lake waters dry up. In the east part, Link can lift one rock and reveal a cave that leads to a Heart Piece. In the north-west corner of the lake, instead, Link can blast a wall with a bomb and get 100 Rupees from inside. Now, switch to a different season to proceed.

The dungeon entrance is visible, but the path is blocked by stone mushrooms. Link needs the Power of Autumn to get through. It's time to visit Subrosia again: the gate is in the southmost portion of the lake.

Subrosian lava lake
From this gate, using various items, Link can go to the Tower of Autumn, just to find it blocked by big rocks. Some Subrosians there need a bomb flower to clear the passage. This item can only be found in the south.

The lava lake can be explored with just the help of the Roc's feather. In its most remote part, Link can pick up a heavy Bomb Flower, but only using the power bracelet.

Tower of Autumn
Bring the bomb flower to the Subrosian outside the Autumn Tower, and they'll clear the passage for you. Get the power of Autumn, then head back to Holodrum.

Autumn on Eyeglass Lake
Back to Eyeglass Lake, switch the season to autumn.

Before entering the dungeon, head back to the entrance of the region. A chest on an islet can now be reached, because autumn filled all holes with leaves. Inside is a Gasha seed.

Now, you can enter the next dungeon.

The compass
The compass is in a room to the west.

The map
Proceed to the east, take the stairs, emerge in another room and continue east.

The magnet gloves
To the west of the map room. Use the magnet gloves to loot some areas of the dungeons, before proceeding.

Mini-boss: Syger
Use the shield to defend from Syger's attacks.

BOSS: Digdogger
Following the "remake theme", Digdogger is a boss from The Legend of Zelda 1.