Combat and gameplay is mostly standard RPG turn based affair while exploring world maps and fighting random encounters in dungeons and on the field. Characters equip between one to three Runes to utilize magic, skills, or support abilities. Magic runes have four spells a piece and use D&D style casting charges instead of standard MP. Skill Runes can be used indefintely but can sometimes cause the character to lose a turn to charge or recover an ability. Support runes have no issues. Parties mostly use six people with the exception of IV and possibly Tiekeris, which use standard four.

There are two unique battle types in the series: Duels and War battles.

Duels are one on one affairs that play rock/paper/scissor style combat where you choose attack, defend, or special based on your opponents dialogue. In a fun subversion of these types of alternate combat syles, your characters levels and equipment actually do determine damage algorithms.

War Battles vary from entry to entry:

Suikoden - Rock/Paper/Scissor mechanic with Calvary/Troops, versus Mages versus Archers. You can also utilize special troops like Ninjas to learn what your opponets next move is for a guaranteed win, Merchants to bribe the enemy on your side, or Dragon Knights to bombard the field with fire. Each army has a set amount of troops and when one side loses all of them the other team wins.

Suikoden II - Turn Based Strategy, Unit type is determined by the character assigned as leader but still follows the lineup from above. You can assign up to three characters per unit which will add to the units stats or give them unique skills like Critical or Evade. You can also cast rune spells to heal units or soften the enemy units up.

Suikoden III - Turn Based Strategy with units built up by allies, but unlike SII, battles are played as as normal battles, but with the A.I. doing most of the heavy lifting. Since the battles do utilize your characters, their levels, gear, and set-ups do matter.

Suikoden IV - Turn Based ship battles where you either exploited elemental weaknesses with Rune Cannons or boarded the ship with party members.

Suikoden V - Real Time Strategy battles with a similar setup as Suikoden II but with the addition of ship battles.

I don't know if the DS or PSP games retain either of these features.

Another feature of the series is castle building. There are 108 characters (sometimes more) to collect in each game and they will bring in new features to the castle like shops or minigames. The real challenge of the series is actually trying to collect the 108 party members as you sometimes have to undertake quests or fulfill certain requirements before the characters will give you the time of day.