|This material is published under the OGL|
You apply your character’s Constitution modifier to:
- Each roll of a Hit Die (though a penalty can never drop a result below 1—that is, a character always gains at least 1 hit point each time he or she advances in level).
- Fortitude saving throws, for resisting poison and similar threats.
- Concentration checks. Concentration is a skill, important to spellcasters, that has Constitution as its key ability.
Any living creature has at least 1 point of Constitution. A creature with no Constitution has no body or no metabolism. It is immune to any effect that requires a Fortitude save unless the effect works on objects or is harmless. The creature is also immune to ability damage, ability drain, and energy drain, and automatically fails Constitution checks. A creature with no Constitution cannot tire and thus can run indefinitely without tiring (unless the creature’s description says it cannot run).
This example assumes max hp on rolls.
If a lvl 7 Wizard Rico the Great has a con of 11 and total hp 28 (so, +0 modifier) levels up to 8, allowing an abilty increase, chooses to increase his con to 12 (now a +1 modifier) would gain a normal d4 hd plus 8 hp (+1 for every level so far) totaling 32 + 8 = 40.