Your soft, flexible mantle is better suited to absorbing light and dampening sound than deflecting blows. You're trained in
Stealth. If you would automatically become trained in Stealth (from your background or class, for example), you instead become trained in another skill of your choice. You also gain the
Terrain Stalker feat, and you can select shallows as a unique option for that feat, allowing you to creep through tide pools, wetlands, and other shallow water.