Forest Temple: the warm light clue

Stand beside the glowing Fairy’s Thought near the ladder and play the Sun’s Song. The warm-light hint in the Forest Temple’s blue room points to a heal. Watch your hearts for the result. To open the nearby sealed door, use the torch and the frozen eye switch instead.

Find the mark in the blue room

1. On 3F, follow the blue hallway to the shifting room. Look for the arrangement where the floor gap is open. If you’re still facing a chained door on the approach, you need a Small Key.
2. Look down near the ladder. Approach the glow and let Navi read the Fairy’s Thought. The message about wanting warm light in a damp room confirms you’ve found the right mark.
3. Stay next to that spot, take out the ocarina and play the Sun’s Song. If you previously walked back into the middle of the room to play, return to the glow and try again.

For a visual landmark, the illustrated Forest Temple walkthrough shows the glow beside the ladder in the blue room. Use that image to orient yourself if the hallway looks familiar but Navi hasn’t offered the prompt.

Do I need the song to keep going?

You can continue through the dungeon without collecting this heal. If the door beneath the frosted eye is your obstacle, line up an arrow through the lit torch and into the eye. Opening that door and answering the fairy are two separate interactions.

I still need to learn the Sun’s Song

The song is taught at the stone monument at the end of the Royal Family’s Tomb in Kakariko Graveyard. Play Zelda’s Lullaby at the Triforce outside the tomb to enter. You can leave this Forest Temple heal for a later visit.

For the path from this room to the fourth flame and the basement, follow the Forest Temple Poe route.

Sources

Power Up Gaming’s Fairy Thoughts list identifies the open floor gap and the healing song. Players discussing this exact room describe the importance of standing at the mark. Zelda Central’s room walkthrough covers the torch-and-eye route.