Islet Cave

The Islet Cave is an optional dungeon in Golden Sun: The Lost Age, which can first be accessible from the Sea of Time Islet in the middle of the game via a trading sidequest. It is notable for its second, deeper portion, accessible only with the Teleport Psynergy at the end of the game, because it is the site of a Mercury Djinni, the best level-grinding spot in the game, and the optional boss Sentinel guarding the summon tablet Catastrophe.

Access and Walkthrough
Access to the Islet Cave is gained by trading objects with animals, which can be found on little islands all over Weyard. To communicate with them, the only means is to use the Mind Read Psynergy. Here is the list of trades :


 * Go to the E Tundaria Islet (located, unsurprisingly, east of the continent of Tundaria continent) and "talk" with Pengus the penguin. Solve the little puzzle in order to save his fiance and he will reward you with the Pretty Stone.
 * Give the Pretty Stone to the bird on the SE Angara Islet (located northwest of Lemuria, east of Champa). It will give you the Red Handkerchief.
 * Give the Red Handkerchief to the cow on the N Osenia Islet (located southwest of Lemuria, north of Alhafra). The Sand Psynergy is necessary to reach it, so you won't be able to complete this mini-quest before completing Gaia Rock. The cow will give you some of its Milk.
 * Give the Milk to the dog on West Indra Islet (located in the stretch of ocean between Gondowan and Indra). It will give you the Li'l Turtle.
 * Finally, go to the Sea of Time Islet, southeast of Lemuria, and give the smaller turtle to the larger turtle, Lonesome George. It will thank you by taking you to its secret spot, the Islet Cave.

The Islet Cave, when you will first be able to enter it, has a small cave-like system that is only accessible at this point. It has to offer the Venus Djinni Meld, as well as a pair of Turtle Boots, which is of limited use, and a Rusty staff that would be reforged into the Dracomace in Yallam (which can be strong depending on how early you can get to Islet Cave). For now, you will not be able to access the second portion of Islet Cave, so return to the turtle to sail back to the main land of the Sea of Time Islet.

Once you gain the Teleport Psynergy in the Mars Lighthouse near the end of the game, return to Islet Cave, because you will be able to use it on the circular pattern at the cavernous portion of Islet Cave to teleport to the second half of Islet Cave. It consists of a series of four linear hallways that have a high encounter rate with the most powerful random monsters outside the random monsters in the Anemos Inner Sanctum. Within this area, you will find the following points of interest:


 * In the second hallway, use the Tremor Psynergy on the shaking statue on one of the pillars to the left to drive out the Mercury Djinni Serac to battle and earn.
 * Among the random enemies are Cruel Dragons, which drop Tisiphone Edges, among the most powerful weapons in the game. They drop the sword with the highest rarity rate, however, with a 1/256 chance to get it normally, and even though felling each Cruel Dragon you come across with the attack effect of an offensive Mars Djinni will dramatically increase the drop chance, it will still be a 1/64 chance, so the Cruel Dragon is one of the most popular targets of Random Number Generator abuse.
 * It is also the place where you will encounter Wonder Birds, the random monsters that yield the greatest amount of experience points of any random monster in the game by an enormous margin: more than 8000 EXP per bird, and this can easily become more than 11000 EXP per bird if each one is felled with the attack effect of an offensive Mercury Djinni. Because of that, the Islet Cave is the only place to go in The Lost Age for post-game level grinding.
 * The optional boss Sentinel awaits the party in the last room, and puts up a strong fight both with its offenses and its immunity to any form of Psynergy. Once defeated, you will gain the Catastrophe Summon Tablet, which is the strongest summon sequence outside the two summons in the potentially miss-able Anemos Inner Sanctum dungeon.

Collectibles
In the "earlier" portion of Islet Cave, these three collectibles are found:

Rusty Staff: In the chest at the upper left of the "main water hall" with the teleport pads, accessed by riding a rolling log from right to left. Take it to the blacksmith in Yallam and he will reforge it into the Dracomace staff artifact. Turtle Boots: In the chest to your left as soon as you enter the "main water hall" with the teleport pads. This is mainly meant for collection and selling for money, since it is far outclassed by a far superior (but still iffy) item called Safety Boots found much earlier in the game.

Meld: A Venus Djinni reached by rolling a log across the water in the vertical "water-hallway" to the right. It must be fought to be acquired.

Whereas the long series of linear halls beyond the Teleport pads holds these treasures:

Catastrophe: This Summon tablet lies at the final room of the dungeon, guarded by the optional boss Sentinel. Essentially, the dungeon's "main" goal and reward, following one of the main optional "superboss" battles of the game.

Serac: This Mercury Djinni is hiding in the shaking statue up on one of the pillars in one of the screens. To make it fall and make the Djinni able to be battled to be collected, cast Tremor near the statue. Precise positioning, and thus several repeated attempts to Tremor the statue off, may be required.