First of all, these changes are largely based on the three concepts below in my signature. I like well-thought-out, not overcomplicated cards that fill in spots.
And the changes:

:
Dagger|Dirk: 0/2. Weapon: Deals 2/5 damage per turn, +1 if mark is

or

. 2/2|5/5 flying.
Short Sword|Longsword: 1/1. Weapon: Deals 3/5 damage per turn. 3/3|5/4 flying.
Hammer|Gavel: 2/2. Weapon: Deals 3/5 damage per turn, +1 if mark is

or

. 3/6|5/7 flying.
Short Bow|Longbow: 2/2. Weapon: Deals 3/5 damage per turn, +1 if mark is

. Ranged. 3/4|5/5 flying.

:
Abombination|Micro Abombination: 5/1

. 5/5|3|5.
Lycanthrope|Werewolf: 2/1

. 1|1. 2/1

: Lycanthropy
Butterfly effect: 3

. Target creature with less than 4 attack gains the ability: 3/2

: destroy.
Purple Dragon|Amethyst Dragon: 10/11

. 10|5/13|6.
Shard of Serendipity| Shard of Serendipity: 2

. Generate 3 random cards/upped cards in your hand.

:
Skeleton|Elite skeleton: 1

. 1/2|2/5. Undead: turns into a random creature/random upped creature when sent back in time.
Mummy|Elite mummy: 4

. 5/3|6/4. Mummy: Turns into a pharaoh/elite pharaoh when sent back in time.
Bone Dragon|Ivory Dragon: 10/9

. 10|5/11|5.
Shard of Sacrifice|Shard of Sacrifice: 2

. Sacrifice all your quanta and 50/40 HP to reverse HP changes for 2 turns. 3 turn cooldown.

:
Chimera: 6/4

. +|+. Combine all your creatures together into one. Momentum, gravity pull.
Colossal Dragon|Massive Dragon: 10/11

. 6|12/7|20. Momentum.
Shard of Focus|Shard of Focus: 5/4

. 0|4.

: Destroy a permanent and gain 0|10. Generate a Black Hole if HP > 30.

:
Graboid|Elite Graboid: 3

. 3/2|4/3. Enters play burrowed.

: Turn into a shrieker/elite shrieker delayed for one turn.
Hematite Golem|Steel Golem: 4

. 4/6|5/9.
Stone Dragom|Basalt Dragon. 10/12

. 8|10/11|13.
Shard of Integerity|Shard of Integerity:
Already discussed here.
:
Emerald Shield|Jade Shield: 4/5

. Shield: Reduce damage by 1/2. Spells aimed at you are reflected against your opponent. Immaterial.
Druidic Staff|Jade Staff: 1

. Weapon: Deal 2 damage and heal 5/7 HP each turn. 2/7|2/8 flying.
Shard of Gratitude|Shard of Gratitude: 4/3

. Heal yourself 5 HP each turn.

:
Ash Eater|Brimstone Eater: 1

. 2/1. /Generate

per turn and when played.
Rain of Fire|Fire Storm: 6/4

. Deal 3 damage to each enemy creature.
Crimson Dragon|Ruby Dragon: 10/12

. 12|3/15|4.
Shard of Bravery|Shard of Bravery: 3/2

. Your opponent draws 2 cards. Draw the same number of cards as your opponent drew.

:
Blue Crawler|Abyss Crawler: 2/4

. 2|4/6|6.
Freeze|Congeal: 1

/1. Freeze the target creature for 3/4 turns.
Trident|Poesidon: 2

. Weapon: Deal 5 damage each turn. 3

/2

: Earthquake. 5|7/5|8 flying.

:
Photon|Ray of Light: 0. 1|1. /Generate

when played and per turn.
Holy Light|Holy Flash: 1

/1. Heal target for 10 HP and gain 2

.
Guardian Angel|Archangel: 3/6

. 2|6/7|7.

: Heal target creature for 5 HP.
Morning Star|Morning Glory: 5

. Weapon: Deal 7/8 damage each turn. Immaterial. 7|4/8|5 flying.
Hope|Hope: 7

. Shield: Reduce damage by N/N+1. N is the number of light emitting creatures you have. Immaterial.
Shard of Divinity|Shard of Divinity: 3/2

. Increase your current and maximum HP by 20.

:
Wyrm|Elite Wyrm: 4|2/5|3.

: Double Wyrm's attack for this turn.
Firefly|Elite Firefly: 3/2

. 3|2/4|2. Generates

/

each turn.
Shard of Freedom: 3/2

. Airborne creatures gain a +25% chance to deal critical hits (+50% damage with momentum) and avoid spells.

:
Fate Egg|Fate Egg: 2

. 0|4. 0: Turn into a random creature/random upgraded creature.
Procrastination|Turtle shield: 6/4

. Shield: Attacking creatures and weapons are delayed 1 turn.
Anubis|Elite Anubis: 5

. 3|6.

/

: Target creature becomes immortal.
Devonian Dragon|Silurian Dragon: 10/11

. 10|5/14|4.
Scarab|Elite Scarab: 2/1

. 2|N/3|N. N is the number of scarabs you have.

: Devour
Eternity|Eternity: 6

. Weapon: Deal 4 damage each turn. 3

/2

: Return target creature back to the top of its owner's deck. 4|8 flying.
Shard of Readiness|Shard of Readiness: 3/2

. Target creature's skill cost becomes 0. Time creatures can use their skill again.

:
Parasite|Bloodsucker: 1

. 1|1/3|1.

: Infect target creature.
Black Nymph|Dark Nymph: 8

. 5|5/7|5.

: Liquid shadow
Shard of Void|Shard of Void: 2

. Reduce the opponent's max HP by 3/4.

:
Immortal|Elite Immortal: 6

. 4|3/5|5. Immaterial.
Phase Dragon|Elite Phase Dragon: 13/14

. 8|6/10|9. Immaterial.
Shard of Wisdom|Shard of Wisdom: 4

. Target creature gains 3|6, and gains spell damage if immortal.
Card I suggest adding:
Comments?