If you have enough mana, you can copy some very big spells in this school, but even copying a cheap removal spell is value enough
When it is not under threat and there is nothing vital to kill, Ajani can lock down anything from a giant threat to a key land while forcing the opponent to find an answer
When it ETbs, you choose a creature type and then it arrives with your number of those you control in counters and that kindred type is increased in size by the counters
If your mana was used for a dork then it gets a permanent +1/+1 boost from a counter, and over time that could be quite powerful
The point was to illustrate the strength of Spell Pierce's effect
Which, as you might imagine, was the framework for the decks Ive prepared for you below