Sundelions are a newly introduced plant in The Legend of Zelda: Tears of the Kingdom that have a crucial role in cooking recipes that counteract the harmful effects of the Gloom unleashed upon Hyrule during the Upheaval. While the Gloom primarily permeates in the underground Depths, players may encounter dangerous Gloom Hands enemies in pools on Hyrule’s surface. Additionally, the entrances to the chasms leading into the Depths are also tainted by Gloom.
When Link suffers damage from the Gloom, not only does he lose health, but his heart containers become cracked, rendering them unable to be recovered or replenished until the Gloom is cleared. Consuming food with the "Sunny" prefix, crafted using 
Sundelions, is an effective way to heal these broken hearts. Sundelions also play a role in quests, including Mattison's Independence and Gloom-Borne Illness.
Where to Find Sundelions in Tears of the Kingdom
To efficiently gather Sundelions, it is recommended to visit the Sky Islands floating above Hyrule's surface as Sundelions grow most abundantly on these islands. Activating the fast travel points for all shrines on the Sky Islands will allow players to easily teleport and regularly collect Sundelions from each island. Therefore, it would be very beneficial for the player to craft a reliable and efficient flying device to travel to any undiscovered islands and reach their shrines.
To enhance their Sundelion farming experience once they've reached a sky island, players may consider constructing a flying vehicle using Zonai devices to make traveling between nearby islands easier. Most larger islands provide the necessary vehicle parts or feature Zonai Device Dispensers where players can obtain necessary devices. Here are some of the best locations to farm Sundelions in Tears of the Kingdom.
South Eldin Sky Archipelago
To reach these sky islands, the player can launch and glide from Eldin Canyon Skyview Tower, located at Coordinates (1637, 1184, 0225), or fast travel to Kadaunar Shrine. Ample Zonai Devices and a minecart rail system facilitate easy navigation between these islands, allowing players to gather 13-15 Sundelions on average. This series of islands is by far the best place to farm a large amount of Sundelion with minimal effort, and the player should return regularly to check if they have respawned.
East Gerudo Sky Archipelago
If the fast travel point at Rakashog Shrine has been unlocked, players can quickly and easily reach these sky islands. Otherwise, they should launch from the Gerudo Canyon Skyview Tower and glide east toward the islands. The flight to the main islands is quite far, so it may be necessary for the player to stop on the closest island at Coordinates (-2230, -2377, 1120). Once there, the player can collect a few Sundelion and take advantage of Zonai Gliders, Fans, and Rockets to craft a vehicle to attempt to reach the large island.
The larger island features a Zonai Device Dispenser, and the lower island offers multiple rocket Zonai devices, which can be fused with nearby parts to create an even more powerful, albeit potentially chaotic, flying machine. The vehicle can then be used to reach the nearby South Hyrule Sky Archipelago and collect a few more Sundelions.
Courage Island
To reach Courage Island at Coordinates (-2212, 0955,1637), teleport to Lindor's Brow Skyview Tower and glide southwest to reach this small sky island, or fast travel to Taunhiy Shrine if unlocked. After collecting the Sundelions, the player can descend to the lowest island, featuring a large round pool, and speak with the Steward Construct to accept his challenge and earn a piece of the Glide Armor set.
The Legend of Zelda: Tears of the Kingdom is available now for Nintendo Switch.