Be warned: most players find minions pretty useless. They essentially cast spells at random, which means they don't intelligently stack blades and traps, don't do a lot of damage compared to a player wizard, don't concentrate on the most vulnerable targets, and worst, tend to use up traps you cast, seriously limiting the damage you can do. In the rare case they actually manage to do serious damage, npc opponents will start targeting them and pretty quickly blow them away. In most situations summoning a minion is a waste of pips that could have been better used for something else.
That said, treasure card minions that do a different damage type than you do, so they don't burn your traps, are probably the most effective. If you like to use feint, though, off school damage won't keep a minion from burning it.
This is a list of the lower level minions given: 1. Storm minion (Water Elemental) - Given at level 18 2. Ice minion (Ice Guardian) - Given at level 28 3. Fire minion (Fire Elemental) - Given at level 28 4. Life minion (Sprite Guardian) - Given at level 18 5. Death minions (14 minions depending on amount of pips spent) - Given at level 28 6. Myth minions (Living Puppet, Troll Minions, Cyclops Minions, Minotaur Minion, and Talos) - Given after completing "Enrollment" quest, level 7, level 18, level 38, and level 55 7. Balance minions (Helpful Mander + Water Elemental, Ice Guardian, Fire Elemental) - Helpful Mander is given at level 18, Elemental school minions, also known as Spectral Minion, is given at level 38
All schools get new minion spells at level 75, which is given by 1. Storm minion (Mokompo Storm Growler) 2. Ice minion (Freddo the Ice Fish) 3. Fire minion (Sir Lamorak Tinder Hart) 4. Life minion (Sir Bedevere Lake Ward) 5. Death minion (Malduit the Devastator) 6. Myth minion (Vassanji Lore Singer) 7. Balance minion (Nerys Barbed Heart)