The Gigas Shadow Heartless introduced in Kingdom Hearts Final Mix. As it's name implies, it's a larger version of the Shadow Heartless and drops the rare Fury Stone synthesis item.

Finding the Gigas Shadow

The Gigas Shadow Heartless is found in the Bizarre Room in Wonderland after completing the story episode there. You will know when Gigas Shadow will appear when the first Heartless that spawn in the area is a group of Shadows.

You must first defeat three waves of Shadow Heartless. Use Thundaga magic to clear them out quickly. When the third wave is defeated, a group of Gigas Shadow will appear.

Defeating the Gigas Shadow

The Gigas Shadow is special in that it will immediately disappear the moment it hits Sora, so avoiding damage is top priority. In order to do so, below are a few methods that can be used, in order of effectiveness:

1. Summon Dumbo right when the Gigas Shadows appear, then use his Splash command to deal damage. For best results, equip the Cheer ability on all party members and equip a summons-boosting keychain like Oathkeeper or Diamond Dust.
2. Use the Strike Raid combat ability to deal consistent damage to the group of Gigas Shadow; this ability gives you invincibility frames as long as it is active. You may have to Dodge Roll in between uses to avoid being hit.
3. Use the Dodge Roll ability to put distance between you and the Gigas Shadow, then cast Blizzaga magic on the group.

Obtaining the Fury Stone

If your goal is to obtain Fury Stones, you'll need to defeat at least three Gigas Shadow in the group for a chance at one. However, you'll have a 100% chance of receiving them if you defeat all seven.

# Defeated	Rewards
1	5 Munny Lucid Shard (10%)
2	10 Munny Lucid Shard (20%)
3	15 Munny Lucid Shard (35%) Fury Stone (10%)
4	20 Munny Lucid Shard (50%) Fury Stone (20%)
5	25 Munny Lucid Shard (100%) Fury Stone (35%)
6	85 Munny Lucid Shard (100%) Fury Stone (50%)
7	85 Munny Lucid Shard (100%) Fury Stone (100%) x2