Hi,
today I want to introduce a simple yet effective tactic with the blue splinter, for everyone who's new to the game.
Summoner: Alric Stormbringer (gives +1 magic attack to all magic monsters on your team)
Tank: Serpent of Eld is really good, because of his high speed and dodge (25% chance to dodge a melee/ranged attack), also has decent health/armor and 3 attack to really hurt the enemy
Backline: Go with every magic attack monster you can fit in (Ice Pixie, Medusa, Enchanted Pixie). If you have extra mana put Water Elemental at last position, it will soak up some damage from opportunity enemies and heal itself
Due to the +1 magic attack from your summoner your monsters will rip through the enemy tank super fast. At low mana battles, once the tank is gone it's usually an easy win, because the backline has little health.
Give it a try.