With the "Illusionary Might" deck, you're going to take the beatdown to your opponent starting on the very first turn of the game. Aggressive creatures like Phantasmal Bear and the Phyrexian mana–fueled Porcelain Legionnaire hit hard and fast. Meanwhile, cards like Æther Adept, Mana Leak, and Mind Control let you control the tempo of the game, ensuring that your pressure holds up even as your opponent attempts to mount a defense.
Spined Thopter and Porcelain Legionnaire let you pay life to get them onto the battlefield a turn sooner, and you should take full advantage of that—your Glimmerposts can gain that life back, after all. Your most powerful card by far, however, is Grand Architect. Not only does it allow your smaller blue creatures to hit harder, but it lets you cast Precursor Golem and Steel Hellkite two turns sooner. If you have the extra mana, you can even use Grand Architect to turn your artifact creatures blue temporarily to get an extra +1/+1!
Against fast decks, you'll want to trade your creatures with theirs whenever you can, either by blocking or by putting the opponent on the defensive. Use your Preordains to get to your late-game bombs as soon as possible. When you're playing against a slower deck, though, be sure to keep mana open to cast Mana Leak to protect your creatures (although nothing can protect Illusions from dying once they've been chosen as a spell's target). This strategy will force your opponent to cast creatures to block with. Then you can either "bounce" them with Æther Adept or drag them over to your side with Mind Control.
Your sideboard can take your deck in different directions. Playing against a control deck full of powerful spells, card drawing, and only a small number of game-winning threats? Bring in Negates, Stoic Rebuttal, and four copies of Neurok Commando, then beat them at their own game! Up against an army of giant creatures that clog up the board? Frost Breath and another Mind Control let you impose your will on the battlefield. Finally, Flashfreeze and Master Thief provide some added value against red, green, and artifact strategies should those show up in your area.
You can also evolve the main deck in a variety of ways. If you max out with four copies of Grand Architect and add some bombs like Wurmcoil Engine and Mindslaver (and maybe a Treasure Mage or two to go find them!), you could be plopping giant monsters onto the battlefield as early as turn three. Alternatively, if you prefer a more swarming approach to combat, additional copies of Lord of the Unreal and Phantasmal Image can overwhelm your opponent with wave after wave of Illusions, while cards like Frost Titan stand by and mop up whatever's left.