mtg cards from the list Collecting reserved Magic: Gathering sets rounded up. Long List of the Ents

Until end of turn, you may play one of those cards without paying its mana cost

Since most of your lands will be swamps, you'll be adding a lot of mana to your pool

It does a hell of a lot for a single green mana

It has Flying, of course, but something more fun is that they actually managed to fit in the flavour of a phoenix by having it be able to regenerate after death -- admittedly, going from the graveyard to the opponent's hand and being forced to stay there for an extra turn is very slow, but the principle of the matter is there

The Omnath, Lotus of Creation Legendary Creature, had the powerful effect to gain four life every turn and draw a card