Execute 3x non-elemental attacks, chance to inflict Sleep (this sleep greatly increases damage against the target)敵に無属性ダメージを3回与え、確率で睡眠状態にする（対象が睡眠状態の時、与ダメージ大幅UP）
Sleep Skill UP Lv4睡眠スキルUP Lv4
On straight+, boosts main card's Sleep skill by 35%親分がストレート以上のとき、睡眠スキルの威力35%UP
|ヒュドラ, ロキ, マーメイド, Priquet|
As one of the Status Effect Girls (Lamia, Harpy, Mermaid) Mermaid is a definite under-performer for most of her life. Despite the description of the skill listed here, from levels 1-5 she actually only applies her status effect to one target, rather than doing any damage. In addition, due to the vagaries of sleep specifically and status effects triggering before attacks (thus meaning the sleeped targets are then going to be hit to likely be woken up), her usefulness is highly limited.
Upon gaining her sixth skill level, however, her ability gets overhauled significantly, as you can see. As non-elemental damage she can hit anyone and everyone equally- including some surprising defense penetration tricks in PvE. However, where she actually shines is the Colosseum. As she is a status effect card, she has a preternaturally high chance of inflicting her status effect- and Sleep is no joke, as is the only status effect that in no form or shape can be played around! Furthermore, her effect now occurs during the attack phase, meaning it can be more likely to stick, and her damage can be very considerable as non-elemental damage against the variety of types and colors of aces you'll see in the Colosseum.
All of this amounts to a card worth considering, especially if you already have her- she won't necessarily wow you like Penguin will, however. Unfortunately, she has no other real uses except being played, being not only her best but one of her only subcards, and conversely being only really useful as a subcard to herself.
|DMG INCREASE(SL6-7 SLEEP)||1.70×||2.00×|
As mentioned above, tragically, Mermaid is her own best sub, and also her only real place as a sub. As she enhances 'sleep type cards,' and not 'the sleep effect on cards,' she can't be used on stellar cards such as Belphegor- the only other 'sleep type cards' in the game are R-level, and you'd be far better served simply playing Mermaid in place of that card than subbing her to it.