You have 17 poison counters on you
you play purify(the spell)
you have +1 purify counters now
all poison eliminated
having a purify on a stick is no different than having 6 purifies in your deck
Actually, the problem is the other way... You have 20 purify counters, your opponent plays poison on you, you still have lots of regen per turn... And that's basically the problem. If its ability costed like and had low attack (3/4, or 2/4 like arsenic), it won't be that OP because of being slow and the fact of not being a killer by itself.
BTW, I mind how it would be to have 6 of this, 6 animated weapons and 6 crusaders in a deck
Then allow me to use Empathatic bond as a better example:
you have a full field of creatures (23 in total)
you are at 1 HP and it's still your turn
you play 1-2 bonds and boom that's 23-46 regen per turn, far more than 20 purify counters
conclusion: bonds > serenity
also, crusaders would make no difference as it applies to
every weapon. you want lots of lobo? 6 lobo 6 crusader 6 flying weapon. You want lots of pulvy? 6 pulvy 6 crusader 6 flying weapon.
I understand that some of these combos may not be very
efficient, but the fact still remains.