Every ability in Teriock Online is mediated by one of four Interactions. There are also several responses that may come into play.
Interactions
Attack Interaction
The most important one os the Attack Interaction, which is used whenever a weapon, body part, or missile would come into contact with a target. The Attacker first makes an Attack Roll (1d20) against the target's armor class (AC). If the attacker is proficient with the ability they are using, they add their proficiency bonus to the roll. If this roll is equal to or greater than the target's AC (typically 10 + AV + P if the target is proficient in their armor), the attack Hits. If the roll is less than the target's AC, the attack Misses. A natural 20 on the die is always a Hit, and a natural 1 is always a Miss. The consequence of a Hit is described in the "On hit" section of the ability that's used.
If the Hit is from a natural 20, then the attack is a Critical Hit and the effect of the ability "goes Critical". If this changes anything about the effect, then it's described in the ability's "On critical hit" section.
Any creature that is up may choose to be hit by an attack, even if the attack would normally Miss. This is called "Taking the Hit". They cannot choose to take a Critical Hit.
Block Interaction
If an Attack Hits, but has not gone Critical, then the defender has a chance to Block. In addition to the AV of armor, every other item has some block value (BV). If the defender attempts an ability that uses the Block Interaction, then they add the item's BV to their armor class. If the new total is equal to or greater than the attacker's Attack Roll, then the Block Succeeds. If the new total is less than or equal to the attacker's Attack Roll, then the Block Fails. The consequence of a successful or unsuccessful Block are described in the "On success" and "On fail" section of the ability that's used. For a Basic Block, a successful Block causes the Attacking effect to fizzle.
Feat Interaction
The Feat (or "Feat Save") Interaction is used whenever a target would have the chance to respond to an ability that doesn't hit them physically (such as area of effect abilities like auras). Any ability using the Feat interaction has a "Saving feature" section which describes which attribute the target must use to make the save. For instance, if an ability requires a "feat of strength" to make the save, then the target will roll 1d20 + STR. If they are proficient in the attribute they are saving with, they will add their proficiency bonus to the roll as well. If the roll is equal to or greater than the "Save DC" then the save Succeeds. If the roll is less than the Save DC then the save Fails. The consequence of a successful or unsuccessful save are described in the "On success" and "On fail" section of the ability that's used. Some Feats may also be able to "go Critical" if the save is a natural 1.
The Save DC depends on the creature using the ability. If they're proficient in the ability, then the Save DC is 10 + P. If not, then it's just 10.
Manifest Interaction
The final interaction is the Manifest Interaction. It's by far the simples and is used whenever an effect "just happens". There's no built in way to deal with a Manifest, only responses like resistances and immunities.
Responses
Resistances
Some abilities grant Resistances to certain effects. Rather than being "absolute" like in live action FanWar, Resistances in Teriock Online have only a chance of stopping an effect.
When a being would be affected by something they are resistant to, they make a resistance save. This is a DC 10 d20 roll that they add their proficiency bonus to if they are proficient in the ability that grants them their resistance. On a success, the target is not affected by whatever was going to happen to them. On a fail, they are. Resistance saves cannot be failed automatically. Only one resistance save can be attempted per interaction. A resistance cannot stop a warded ability.
Immunities
If you are immune to something, it does not work against you at all. A warded ability does not cut through immunities.
Order of Operations
As a rule of thumb, the basic rules of Interactions happen first, followed by Immunities, then Resistances. In case it's needed, the complete interaction routines are provided below.