In deck building, you need some very important card that can't be replaced by other cards. Here are some of them.
Walls: Some say they are very important, for me they are not that important. They almost always force opponents to let them go through or use many pillz just to beat them
ex. Zatman, Nanook, Rowdy
Damage Reducers: One of them most important cards in deck building. They are mainly used for defend/bluff purposes. There are also some of them who are very good finishers.
ex. Uranus, Gabrielle, Charlie
Stoppers: They are also one of the most important cards in deck building. They stop your opponents abilities and bonuses and they can attack very well.
ex. Otakool, Jackie, Splata Cr
Heavy Hitters: They are inddeed the MOST important card in a deck. You can't play offensive w/o them, they have damage of 6 and higher.
ex. Vickie, Shakra, Rowdy
and the best thing that you need is not a card, it's called "strategy".
good games to you all!
Life Stealers: They inflict damage to Gain HP for the player using 'em. Can also be a bluff card. USUAL characteristics of the Life stealers are: Decent Power (5-6) and very low damage to balance the life steal. Also some are very scary when Fury'd. Most of the life stealers are from Nightmare. But note that they can easily be beaten by SoA! So don't rely on them always.
Good Examples are: Kenny 6/3 +2 hp per damage (very scary!), Ielena 8/3 +1 life per damage (medium scary), Hel 6/2 +1 life per damage (low scare factor)
Heavy Hitters/Powerhouses: They Damage your opponents life to half or MORE than half. They have massive Power and Damage and they can only be defeated by Attack Reduction or Power reduction. They usually have 4*-5* and has the ability/bonus that can reduce the opponent card's Power or Attack, which is really good for a 5*. They usually rely on their Power and Damage. And if they have an ability/bonus, it's USUALLY -attack or -power to the opponent or +attack or +power to their self. There is also an element of scare tactic in these cards. You can bluff with them but who would waste such massive Power and Damage
Some Examples are: XU52 6/8 -8 attack SoA (Scare tactic), Bodenpower 7/7 -5 attack +2power (Very scary because of 9 power!) Blaaster 6/6 -2 power and +2 power (virtually a 10/6 card)
NOT YET FINISHED!
Courage Cards: These cards have very useful effects of abilities but to balance their abilities, they have to be couraged. The courage means that their abilities are only activated when played first. Courage cards are very predictable which is the only disadvantage when using 'em. The USUAL courage abilities are SoB or + Power or -Damage.
Some examples are: Shakra 8/6 courage: SoB and can be a FULL STOP card when played first, Edd 7/5 courage:SoB and -12 opp. attack ( Very useful against nightmare, Especially Kolos ), Kerry courage:SoB and +12 attack in Monoclan
That's is all.....I think... Hope this Helped...
1 more thing....
Support cards: These cards are very useful in a Monoclan deck. The USUAL characteristics of support cards are: they have low power/damage. The USUAL effects of supports is to +atk or +power/damage.
Examples are: The Rescue Clan support +3 attack, emeth support +5 attack +2damage (scary when in monoclan)