When held by <a href="http://pldh.net/dex/move/monster/clamperl" class="linksred">Clamperl</a> its Special Defense stat is boosted to 200% of normal.
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If Clamperl holds this item while being traded it will evolve into <a href="http://pldh.net/dex/move/monster/gorebyss" class="linksred">Gorebyss</a>.