The two great strengths of the Phantasm mages are their creatures and their incredible capacity to adapt to any given situation.
Most of the more powerful and effective phantasm creatures have relatively low rank in comparison to similar creatures of other colors. For example, elementals do not affect the rank of phantasm mages anywhere near as much as red dragons affect the rank of eradication mages. This means that you can have superior creatures, and be ranked with opponent mages who often field relatively weak armies. Taking land will therefore be relatively easier.
Note that having elementals in your first stack will NOT be an effective method.
It was suggested to me that a stacking of:
Archangels-Mindrippers-IceElementals or Mindrippers-Archangels-IceElementals might be the way to go but I have no confirmation on that so I advise you ask our top Phantasm mages on their views.
Phantasm mages also have the advantage of the spell enchantments Hallucination and Mind Bar. Hallucination prevents many attacks upon your lands. It can be terribly annoying to attempt to mass pillage a blue mage who is using Hallucination, with as many as half of your attempts ending up as wasted. The potential of Hallucination also often keeps nether mages from deviling phantasm mages. An attack on a hallucination is regarded to be an attack by most guilds regardless whether it has been succesful or not. Thanks to Mind Bar, phantasm mages do not need to keep large numbers of barriers but can still enjoy magic resistance.
The greatest weakness faced by the phantasm mage is the high reliance upon one single resource - mana. Since mana directly yields all of the benefits described above, maximizing your mana production is a necessity.
There are only two ways to do this, and the first is to have lots of nodes. Experienced phantasm mages usually have 39.99% of their acres built into nodes. It is very important that you do not reach exactly 40% or higher, as magic point production is very negatively affected. The second way to boost your mana production is by hiring a verdant hero Shaman (level 16 or higher) or a nether hero Crypt Keeper (level 18 or higher). They have the power of Channeling, which increases your magic power production. Phantasm mages of high rank will nearly always be running at a relatively high negative magic point production, sometimes as high as -18,000 magic points per turn! But all mages regardless of colour must operate with a high negative on some resources if they want to be ranked high.
Perhaps the best defensive spell and item combination a phantasm mage can use is Fog Cloud and Satchel of Mist. Each reduces the damage dealt by attacking and defending creatures by -10%, for a total adjustment of -20%. Since the success of land grab attempts are based on damage dealt, this combination alone stops several instances that would otherwise result in lost land. Equally attractive is that Satchels of Mist are usually cheap to acquire! Another item favored by phantasm mages is Monkey Brains, which enhance psychic-type attacks.
I contend that the overall best hero for phantasm mages to use is the Bard. Bards randomly increase one of your stacks attack ability by 10% while simultaneously decreasing a random enemy stacks attack ability by 10%! If you're fortunate enough to acquire three or more bards, your defense is nearly impenetrable when used in conjunction with the Satchel of Mist/Fog Cloud item and spell defensive assignments. Your enemy units overall combat ability can be decreased 30% or more while your own overall combat ability will be unaffected by your spells and items!