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Related topics: Stamina Regeneration
Starting stamina is determined by base Endurance at creation. Stamina can be raised directly as well as indirectly by raising Endurance (one point of Stamina per point of Endurance). Stamina regains slowly over time, very slowly in combat mode, decently if in peace mode (even if running!), faster if crouching (x2), even faster if laying down (x3). Augmentation Gems can double and triple the rate of regeneration when laying down (stacking). Stamina can be restored with Life Magic and with various Potions and some Foods. Of these, loot Philtres are generally the best.
Maximum unbuffed Stamina is ?? and the current theoretical maximum is ??.
A high Endurance also increases the amount of stamina regeneration. Higher maximum Stamina also increases regeneration rates.
Stamina is buffed by several items. The most common ones are the +200 stam bonus from the Platinum Spirits and the rare creature drop quest item Telumiat Hollow Minion Essence/Potion of Endless Vigor. Ulgrim's Contest Mug, a housing Item, also gives you a +50 Stamina bonus, stacking, when you use it (and have completed the quest), and Warrior's Vigor is a Cantrip stamina buffer at various levels, as is one of the Potted Plants Housing Items.
Stamina is a key fuel stat for Melees and Archers in combat. Using a weapon or drawing a bow burns stamina every time you use it, with the heavier weapons and bows burning up to two or three times those of lighter weapons. The cutoff limits on Stamina for weapons seems to be 700 bu = +1 stam burn at midbar, 1200 = +2, and 1600 = +3. These amounts are increased to double at Full Power and to 1/2 at minimum power (to a minimum of 1 Stam with every swing). A higher Endurance decreases the amount of stamina lost when swinging a weapon on an improving % basis. These changes were implemented because non-mages were frequently running out of Stamina in combat, a condition a casting mage never had to deal with. With the changes, Stamina lasts much longer for weapon-wielders.
In addition to losing Stam when swinging a weapon, a point of Stamina is lost when you evade a melee or missile attack, and 1 pt is lost every time you are hit (or that you hit something, a key tactical move on high end monsters!). A high Endurance can negate the stamina lost from a missed attack on you, again on a rolling % basis that improves with your Endurance score.
Stamina is actually probably even more key for Mages. The standard tactic to refreshing your Mana is to use Stamina to Mana, and the maximum amount you can convert is based off of how much Stamina you have remaining. A high Stamaina number means you can get back a tremendous amount of mana in one spell. This spell is also used at many levels to regain mana when buffing spells. Stamina to Health is actually the single biggest healing spell in the game if used for emergencies. A common magic item used for this purpose among those with no Life Magic is Ulgrim's Contest Mug, whose Signature Spell is Stamina to Mana 4.
The Healing skill runs off of stamina. Basically, for every 5 pts healed, you lose 1 stamina. Thus, healing yourself frequently exhausts you, and with no stamina you can also no longer heal.
If you have no stamina left, your melee and missile defenses drop to 0 (and those of monsters do, too!), insuring that you are automatically hit. You are incapable of swinging your weapon to effect, and suffer -50% to your weapon skill unless you can pay the full stam cost of your swing (if you are at 0 stam, move to fastest weapon speed immediately, as it burns the least amount of stamina). Thus, one way of killing a monster hard to hit is to drop its stam to 0, insuring that it won't evade you. This is a particularly effective tactic on the Aerbax quest, as it allows Archers to fire at full speed and not miss, effective quadrupling their damage output.