Seething Slug

Head to the Zaqali Caldera in Zaralek Cavern. The Seething Orbs and Seething Cache are spread across the area roughly between 25, 44 and 37, 55. Be aware that Dragonriding in this area is actively contested by knockdown effects, so manage your Vigor carefully.

Search the Zaqali Caldera for three Seething Orbs and click each one to build your buff. Known orb locations include: at 28.75, 55.3 — at 29.95, 47.97 — at 34.41, 45.71 — at 36.2, 44.01 — at 31.18, 51.95 — at 30.2, 40 — at 27.7, 49 — at 26.7, 47 — at 25.24, 44.8 (behind the large altar across the lava) — at 27.9, 51 (around the altar) — at 29.02, 41.94 — at 29.15, 42.5 — at 35.83, 41.4 (behind a plant) — at 32.82, 52.13 — at 35.63, 48.77 — at 37.58, 46.76 — at 32.73, 52.23 — at 31.2, 51.9 — and at 35.45, 41.

Once you have collected three orbs and have your buff active, fly to the Seething Cache at 32.33, 39.35 and loot it to receive the Seething Slug. Do not Hearthstone or disconnect before looting, as either action will remove your buff and you will have to start over.

Avoid realm-hopping while attempting this. When the Seething Cache is looted by any player on your shard, it despawns and removes the buff from everyone else on that shard. Staying on your own realm rather than hopping to others has proven more reliable for a successful loot.