A new portion of cards ideas.

[Sabaku]

Nocturnal bond
Permament
Both you and your opponent are dealt 8 damage for each creature they summon.

Merge
Spell
All of the opponent's creatures on the battlefield are merged into one creature whose attack is the sum of all the creatures' attacks, hp is the sum of all the hp, yet halved and skill is a random one.

Double-edged healing
Spell
Both you and your opponent are healed 50% of their current hp.

Ultimate freeze
Spell
Freezes a target creature so rapidly that it may die immediately(inspired by Bloons TD series )

Predator
Creature
Once summoned the creature starts hunting (devouring) random creatures on the field (yours and your opponent's). Each prey the predator hunts down increases its attack by 50% of the killed creature's attack. The attack it aquires is released to strike the opponent as soon as there are no creatures left on the battlefield.

[ScytherLoL]

Some good ideas there you have. Thankyou for posting them. Now to the cards;

Nocturnal Bond:
Is it possible to think that Darkness/Death Creatures are not affected by this card being Nocturnal themselves and if that is the case what about a simlar card for other alignments (ie. Sunlights Rail: All creatures except Light/Life)

Merge:
I don't really like this one but only because it says Opponents Creatures, change it to target creature then you can use it on you (ie Aflatoxin therefore 23|12 Creatures)

Double edged Healing:
I am unsure why you would want this card at all. What benefit can be had by using this?

Ultimate Freeze:
A nice idea. But I will cover costs soon.

Predator:
A Random Devour creature? We are trying to get away from Random but this creature has its plus points. His attack vanishes if he has no prey?

OK so just a couple more points on all your cards:

1. You have no costs for any of these. You need to post a cost with them regardless of high or low then we can help establish OP or not.
2. No elements for these. ie PRedator although has Devour would most likely be Entropy the element of Random but is it?

2. Creature Stats. OK so what does Predator start out as a 1|2,1|5,0|5 or something like that.

These points just make it easier for us to understand your cards and how they can be used.

Thanks and keep up the good work

Scyther

[Oooh Muffin]

Nocturnal bond
So you have to rely on heavier creatures... ok

Merge
This and congeal may be a bit powerful, if it is played more creatures after the merge, what happens?

Double-edged healing
If I understand this right, it's better to have more hp? 2/3 of HP = full heal?
if so I don't see the use of it. Maybe you have some ideas?

Ultimate freeze
Have played bloons TD myself,
the card: Instant kill is maybe a bit powerful, and we already have the ice bolts

Predator
This one should be easily killed, or I think it will be overpowered

But good job, how do you all come up with all of this xD

[Glitch]

Merge + Parallel universe =  ???

[bobcamel]

No costs, no elements, no way to comment. Give some of those.

[Sabaku]

Okay, so let me provide it with some further details. Here we go.

1.
Name: Nocturnal bond
Type: Spell
Element:    OR  (I'm not yet quite sure)
Cost:  OR 
Effect: You and your opponent are dealt 8 damage for each creature you summon (creatures stay intact, dmg is directly aimed at the players).
What is it really for? The idea behind this card is to prevent spamming of creatures at will. Every step will have to be double-checked, so it is really profitable for you to summon another monster. I believe it would be even better if this card could affect only the opponent, not the player, but well, it's all to be figured out.

2.
Name: Merge
Type: Spell
Element: 
Cost: 
Effect: All of the opponent's creatures on the battlefield are merged into one creature whose attack is the sum of all the creatures' attacks, hp is the sum of all the hp, yet halved and skill is a random one.
What is it really for? I want this card to be found useful at situations such as when having tons of creatures on the opponent's side and you can't affect them all with your spell. If so, you merge them into one monster and voila! - you for instancce have just used poison spell at them all at once. Possibilities are surely numerable. And yes - you could use it on both yours and your opponent's critters.

To be continued...I gotta go.

[bobcamel]

Now that's doable.

Nocturnal Bond: It has to be a permanent to take effect every time a creature is summoned, spells are more like "players get 8 damage for each creature on their own side of the field". I'd say the damage is a bit high, for you can have multiples of those things out and then summoning anything is deadly... also, I take it that creature creation via Gravyyard doesn't count, otherwise you'd have a nice suicide with Skeletons and those. Bedsides, nice card.

Merge: Or mutate them all at once into a single Abomination/1/7 Graviton Fire Eater with Dive. Too strong.