Interesting card, I honestly think that the cost should be lowered to 5
for upped.
A good counter against growth creatures and usable on your own creatures if they are anti-mattered, a constant heal source though for 3
, it really depends on the creatures attack size prior to it being anti mattered to be worth wasting on it, rather than damaging.
though i doubt it would be used for such reasons.
pretty good idea though, especially if the opponent is spamming dragons on the field.