something someone told me not so long ago, you should fill all spaces in the grid while making a card, and only use public domain art, your own, or art you have permission to use
frozen shard: too powerful
nefarious gate: you don't upgrade cards ingame, and you should give the gate some use before its upgraded
necromancer: 4/5
necromancer lord: 4/6
shadow demon /elite shadow demon: the idea is good, but normally if you make a creature me powerful you don't make it cost less
SD: cost 8
ESD: 12
solar burst shield: you should say how much the creature is debuffed, in ay case, its insanely powerful, have in mind that Fire Shield is way less powerful and costs more
storm: could cost a bit less
zombie: could cost 3 or 4 having in mind it requires another
Zombie horde: you made it a permanent
forest shield: my favorite card of your collection
leviathan: i like it, but having in mind it can kill almost any creature, it should cost more OR you should make it only able to eat creatures with less hp
artifice: has no connection with the upgraded version of it, you should make then 2 different cards
octadic: raise cost to 7
pilfer: should cost way less, also, i don't know if there is or will be a way to search your deck
vivid orb: i like the idea, but its too powerful