If there were to be a shard repair shield, there would be a shard destroy spell as well.
Thus, you would be in a constant counter spell battle with the Sorcerer King. Now, I don't think this is a bad idea, but if we get to heal them with magic, then he should get to destroy them with magic.
I would prefer to see a shard shield spells instead of "heal" spells. Where you cast magic to shield the shard from the attack as magic is not directly affecting the shard it is only attacking the units around the shard instead. This spell is not the end all. Instead, of full damage to the shard, maybe half the damage instead. But, I think this would be still challenging and won't stop the impending doom, just delay it a-little so you can reach the shard.
The enemy could them send shield breaking units whose sole purpose is to counter the shield, but have weak damage and hit points, but are magical in nature. But with one of these Sorcerer King units, the shield is ineffective and dissipates immediately.
I would like to see some crystal wall towers. Build two towers within 5 tiles, then the land between them becomes a magical shield. Doing heavy damage to units that pass through, but are immediately destroyed by these weak anti-magic shield units, at possibly the cost of that unit, but not guaranteed to lose that unit.
I would also say this shield works both ways, you can't go through it either without the same damage or destruction of the shield.
