Quest Chains and the Rewards They Gate

The long chain is Sage Yijiu on Battlefield Isle. Five quests, in order, end at One Hook Dominance. Two rod-seller quests unlock Cryo Gravity Rod and Soul Thorn Rod without paying the sticker price. Several NPCs give one skill or one orb.

Sage Yijiu on Battlefield Isle

1. Diamond Rod. Catch 5 fish of at least 1.5M kg. The rod has no listed Power or Luck. It gives +50% damage to Cloud Ascension skills.
2. Phoenix Annihilation Art. Own Phoenix Strive Art v2, catch fish 250 times, and catch a Scarlet Fish and an Elder Scarlet Fish of at least 1.5M kg each. Both Scarlet fish spawn in Thunderstorm on Bamboo Isle. Phoenix Strive Art v2 is named as a requirement and is not given its own row in the 37-skill table.
3. Fivefold Ascension. Catch a Draconic Koi of at least 2M kg, own Sever The Gate v3, and catch 10 fish of at least 1M kg.
4. Tenfold Convergence. Catch a Rainbow Dragon Fish of at least 6M kg and use Fivefold Ascension 50 times.
5. One Hook Dominance. Catch a Frost Kingfish of at least 5M kg, a Frost Queen Fish of at least 6.5M kg, and use Tenfold Convergence 100 times.

The weight gates climb faster than the skill list. Your rod, not another shop purchase, is what clears them.

Rod-seller quests

Frost Isle pays the Cryo Gravity Rod: fish 100 times on Frost Isle, catch two Primordial Kunfish Overlords of at least 1M kg, and catch 4 Primordial Kunfish. The rod is also 8M Cash.

Coconut Isle pays the Soul Thorn Rod: three Mutated Koi Whales of at least 1M kg, 5 Warbringer Sharks, and 5 Dreadscale Groupers. The rod is also 20M Cash. Spawn conditions for those quest fish are not published beyond the quest text.

One-reward NPCs

Giang Lao on Bamboo Isle gives Shadowless Taji Strike. The same name on Battlefield Isle gives Ascended Taji Art. Ha Dieu De on Frost Isle gives Sever The Gate v3. Lao Ngo gives Heartbreaker Cleave V2. The Blind Grand Angler gives Astral Grand Art Zenith. Bac Minh on Coconut Isle gives the Bac Minh Orb.

Skill damage upgrades are a different NPC, Skill Upgrades, and they spend Essences. That is not the gate-line quest.