Use 8 runes to summon 8 powerful magical beings to defend your Ancient Tree. Match 3 or more runes to replenish mana pool from which to summon your guardians. During battle, you can use druid help - they heal your guardians or remove runes from the screen - but after every action they need time to regenerate.
Match 3 (or more) identical sybols to gather runes. Once the bar is full, you can summon a magical creature. Place it on the lane you wish to defend. Use magic of Druids to heal your Creatures.