|System Reference Document v3.5|
To create a variant list, simpley start with the standard list of monsters and add and remove creatures og the appropriate power level. This allows an infividual spellcaster access to a much smaller number of monsters at each level, but the spells remain versatile and effective.
Without a goal in mind, however, this procedure tends to create a very haphazard list. Start with a basic concept, or theme, to guide your selection. Choose a theme from those listed below or make one up yourself. Once you have a theme in mind, try to limit your list only to creatures that fit the theme.
Sample themes include alignment (law, chaos, good, evil), base creature type (such as animal, elemental, fey, or outsider), creature subtype (such as fire or shapechanger), and template (such as celestial or fiendish).
Simply choosing a theme like this doesn't always yield a perfect list, occasionally leaving a level without a suitable monster. As long as you can find a template that fits the theme, though, you can solve this problem. Simply choose a base monster and apply the template that fits the theme, then compare the monster's adjusted CR, Hit Dice, and special abilities to the monsters available at the spell level. If the monster seems to match the power and abilities of the monsters at the same spell level in the standard lists, it's probably ok to add the monster to the themed list.
For example, when building the sample earth themed list below, there was only one monster from the existing summon nature's ally V list that fit the theme (the Large Earth Elemental). Although the ankheg is a magical beast not normally subject to a summon nature's ally spell, its burrowing and acid spit abilities made it a natural for the list. Adding the earth creature template from Manual of the Planes brought the ankheg to the proper power level. In addition, adding the template provided a stronger link with the theme of the list.
Sample Shemed List: Stone/Earth
Sample Themed List: Heavens
Sample Themed List: Fiendish Gnoll
Add one monster to one summoning list whenever access to a new spell level is gained. Most characters using this option won't have more than a couple of monsters available for each spell. Most favorable for characrers with access to a number of summon spells (such as clerics and druids).
Add one monster to each summoning list whenever access to a new spell level is gained. Characters using this option have the most monsters available for their lowest-level (or first gained) summon spells, and fewer for those spells gained at higher levels. Most favorable for characters with access to a number of summon spells (such as clerics and druids).
Add one monster to one summoning list to which the caster has access (or knows, for characrers with a limited number of spells known) whenever a new spellcasting level is gained. Similar to the second option, but each list is about twice as long.
Add a monster to the appropriate summoning list whenever the charater witnesses another spellcaster summon that creature. With this variant, the DM might also require a successful Spellcraft check (DC 15 + Spell level) to learn how to summon the new creature.
Sample Individualized lists presented below were generated using the "add one monster to one summoning list whenever a new spellcasting level is gained" procedure. Both spellcasters gain access to a 9th level summoning spell at 17th level. Because of this, it's best for them to simply pick a monster from their highest available list at levels 1st through 17th. However, because the number of 9th level spells they can cast each day is severely limited, they are often best served by adding monsters to lower-level summoning lists at class levels 18th through 20th. This explains the strange order of levels at the end of the individualized summoning lists. For example, when the dwarven cleric below reaches 18th level, he has access to only two 9th-level spells per day. Although he prepares the summon monster XI spell nearly every day, the elder earth elemental is the best possible choice for him in nearly every combat, and adding a new monster to his summon monster IX list doesn't help him much. Instead, he adds the celestial dire tiger to his summon monster VIII list.
Sample Individualized List: Dwarven ClericA dwarf cleric with a penchant for melee combat, he has had considerable success in using the first round of combat to summon a physically powerful monster and then wading into combar beside it. His individualized summoning list is described below.
The list below was constructed using the procedure in which the caster gains access to a new monster on one summoning list each time he gains a level. With this dwarven cleric's tactics and personality in mind, the first monster taken at any spell level is a large, physically powerful monster. Subsequent monsters at the same spell level tend to have more versatile movement and spell-like abilities.
Sample Individualized List: Halfling DruidA halfling druid who favors ranged combat from atop her long-time riding dog animal companion, she prefers to summon mobile monsters capable of keeping up with her mount's speed and fast enough to stay between her and her opponents in the midst of a running battle.
The list below was constructed using the procedure in which the caster gains access to a new monster on one summoning list each time she gains a level. With this halfling druids' tactics and personality in mind, the first monster taken at any spell level is a swift animal, usually one capable of flight. Subsequent monsters at the same spell level tend to be larger quadrupeds capable of serving as temporary mounts.
A lot of this variant's potential to enrich the game requires that you differetiate summoners along specific lines and assign each a different list, lending a specific flavor to each group. Here are a few ways in which you can categorize spellcasters who use summoning spells.