The level and type of monsters summoned is:
1. Dependent on the depth and/or level of the summoner. For example, summoning monster at 200 feet down will almost always only result in Goos, Kobolds, Goblins, Rats, Cave Spiders, Garter Snakes and sometimes Orcs. However, every once in a while, a higher level monster may appear. For example a Wicker Man. (some testing done, more testing needed)
2. Firing at an enemy spawned by investigating doors to little rooms (under the conditions listed below). This results in a 95% chance of the same monster being spawned. This can be used create many rare items early in the dungeon.
The theory behind why this works is because the little rooms create a spawn point for the specific enemy in the immediate area around them once activated (the doors to the little room open, and will show up as red on the mini map). Under normal circumstances, the room will spawn around 5 enemies before going dormant. You must use the wand of create monster before the room goes dormant, or you'll go back to the normal enemies being generated. Note: the doors in the gnome mines will not work for this.
A great reason for doing this is if you're playing a spellcaster. If you find a door that spawns kobold shamen, they can drop spellbooks.
Be aware that enemy creation is exponential (each white dot you see along the beam where it connects with an enemy will create another creature!). It is very easy to end up with 40+ creatures trying to kill you. I highly suggest you are at full health and hasted if at all possible. The spell wizard lock is invaluable for freezing huge groups of enemies like this.
StrategyEditWhite Witch or Huntsman characters can learn the Beast Mastery talent that allows all summoned monsters to have a chance of being tame, up to a 100% chance with the third tier of the talent. This can be used to create and invinsible army, if the Player has more than one Wand of Create Monster. A bard has his lute to mesmerize them. Be carful if there's a lot of it. Polymorph them and play your lute. Something like beetles maybe can't be easily snapped out of it and they will conflict haste.
Summoing a creature can be used as a means of attempting to generate food loot in times of desperation by reading the scroll, killing the creature, and hoping it drops a food item.