She's a human wizard that discounts the first spell you cast with X in its mana cost by 1 for each +1/+1 counter on her
In the case of Sazh's Chocobo, when a land hits the battlefield, it gets a +1/+1 counter , meaning that the more lands you can play each turn, the more counters it gets, and despite starting as a 0/1 creature, it can become quite the hulking beast very quickly
Hydras are cool anyway because a lot of them have X as part of their casting cost, and that means theyre basically always on curve
The combination of a fragile body and additional setup steps has mostly kept this card out of the top tier of Legacy, but its never far from that level
Wizards of the Coast has been printing fixed versions of Reserved List cards ever since the Reserved List was created
Thinking about your side of the field, cards like End the Festivities, Forked Bolt, and Play with Fire are burn spells that are very good to deal with convoke decks or small creature/weenie decks, while not being useless against midrange or control
