it would still see limited use, even if it were up to 15. how common are 10+ atk creatures, and is doing (up to) 15 damage once worth 5 | 3 ? creature cards with a decent atk|cost ratio would outperform it majorly. leaving the only justifiable use in decks where
is used, essentially making it a 1 | -1 net cost card for the damage done.
basically as a result, i think it is a good
card idea, but maybe not a mechanic suited for a shard