Not only does it add a +1/+1 counter to your creatures that deal combat damage to a player, synergizing nicely with Tidus, but it also gives all creatures you control with counters trample and reach, which are powerful abilities
There are a couple other theories floating around though
(Damage and effects that say destroy dont destroy them.) This is the source, the line unbroken since the calamity that brought such monsters to our shores. Hastric, Thunian scout Illustrated by Aleksi Briclot Standard Not Legal Alchemy Not Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
If youre self milling a lot then maybe you want Timeless Witness, and there are effects like Unnatural Restoration that lend themselves to counter-based strategies
Ultimate Magic: Holy Ultimate Magic: Holy feels like it should be higher on the list from the perspective of Final Fantasy , but, honestly, Im kinda disappointed