Brainstorming:
: Going back to the original ideas about Mermaid: Song/Magic of Mermaids: Target creature is under the magic (of the song) and does not attack, until (this) Mermaid successfully attacks. (the creature would have 2 | 1 attack, so it is useful against decks with shields. Would this be too limited? For the upped version, any shield with DR 1 or more will give a perfect combo.)
Warden already has this effect but better.
: Explore (Good intentions to bring humans down to the secret kingdom): Target creature's attack is doubled for 2 turns, but then takes damage equal to the extra attack gained (going down to the amazing kingdom is great, but you drown after a while... )
Sounds like Fire (Rage Potion)
: Name (with the intention of drowning someone): Target creature with lower HP (lower than the HP of this mermaid) takes damage equal to the difference between the HPs. (this would require careful balancing with the HP. Would this be a working mechanism? Some form of CC related to the HP of both creatures.)
Devour is a better version of this. Draining hp would fit Darkness better. Drain 1 full hp gain +0|+1?
: transparent: Cannot be targeted by spells, but would be affected by mass CC. It's a nerfed quint, I know... But would give a chance for a higher stat creature and still some protection.
Or a bit of combination of gravity pull and lobo? ??trap: gravity pull. Attacking creatures are lobotomized.
Perhaps a temporary immateriality?
Name of ability(needed)
Ability: All effects on target creature are inflicted to *insert name of creature* as well.
This would work with all positive effects for the upped version. Also I'm thinking about making this a both way version, so if your creature is damaged the creature, with which it is linked is damaged as well. It would be really useful with Growth and positive effects for your creatures. (All abilities affecting the creature, all spells would work as well. If you target a Phoenix, this creature turns into Ash as well. Ash turns back to a phoenix, this creature is back to a phoenix. The cards are connected as long as they're in play)
Sounds a bit complicated, but it's simple I think.
See voodoo doll in the Reliquary