Summoning monsters, according to the game world in Dark Summoner, is accomplished by transporting monsters in from alternate dimensions in order for them to do the Summoner's bidding. This has directly and indirectly led to the destruction of the world as we know it, making the world of Dark Summoner a bleak, post-apocalyptic wasteland, controlled by the three powerful Guilds.
Practically, it is the mechanic by which players can (usually randomly) summon more-or-less powerful monsters to add to their collections.
There are several different types of Summons: (Note that relative odds of receiving different tiers have not yet been calculated for the various types of Summons. Please inform us of any research done, either in the Talk page or by adding directly if you have statistically significant data.)
This is by far the most common type of Summon that a player will encounter and use. It can be obtained through Ally Points, daily bonuses, stamp collections, social bonus and other special events.
Type of monster summoned: C-rank through A has been observed at this time.
Note: Please note if you have obtained a higher-rank monster than A on the Talk page
Type of monster summoned: B-rank through AAA has been observed at this time.
Note: Higher rank monsters (AA-AAA) appear VERY infrequently so players should not expect to acquire one of these monsters with ease. That being said, there have been reports of players acquiring AAA rank monsters through free dark summons obtained in events so there is still the possibility of obtaining these entities.