The Elixir of Life
Prerequisites for prestige classes, weapons, and other characteristics within the game must be met at the time of acquiring that specific item or characteristic, which are checked as soon as the character has a chance to act. However, one may retrain any of those characteristics afterwards following the retraining rules listed in the Player’s Handbook II with the exception that that player must have gained one full level with the prerequisite before retraining it. That player may then retrain the prerequisite at the next level.
Feats may be chosen if the player does not meet the prerequisites for the feat, but the feat cannot be used until the player has met those prerequisites. If the prerequisites for the feat are able to be retrained, that player may retrain them following the above guidelines.
Ex: Rebecca, the 14th level wizard, wants to take the Archmage prestige class at level 15. She has not yet taken the Skill Focus (Spellcraft) feat. At 15th level, Rebecca gains a new feat. She takes Spell Focus (Spellcraft) feat, and now meets the prerequisites to take the Archmage class. Because characters do not “act” as they level, she may now choose to take the Archmage prestige class at level 15.
Ex: Billy the barbarian is on a dungeon crawl, and is battling a cleric in one room, while an ettin in another room attempts to smash down the door. Billy then defeats the cleric in melee combat. The cleric possessed a wand of Inflict Serious Wounds, which Billy promptly takes. Billy is not trained in Use Magic Device, so Billy may not yet use the wand, even though the battle with the cleric would certainly yield enough experience for Billy to acquire a new level, and therefore be able to spend skill points on Use Magic Device. If the DM allows players to level-up before the ettin smashes down the door, Billy may use the wand once he is able to act.
Ex: Johnny the, 2nd level ranger is hoping to acquire the feat Precise Shot. At 3rd level, he gains the feat Point Blank Shot, a prerequisite to Precise Shot. At 6th level, Johnny gains the Precise Shot feat. Johnny cannot retrain Point Blank Shot at 7th level, because he has not yet gained one full level while meeting the prerequisites to Precise Shot. At 8th level, Johnny may retrain Point Blank Shot if he so chooses. He may not, however, also retrain skills, class options, etc. because he may only retrain one aspect at any given level. Johnny can’t later take the Far Shot feat, because he no longer meets the Point Blank Shot prerequisite.
Ex: Jessica, a 9th level Bard, wants to take the Mobility feat, but she only has a DEX score of 12. She may take the feat, but she cannot use the feat until she has a DEX score of at least 13, provided she also has the Dodge feat. If her DEX increases (due to a magic item, a spell cast on her that increases her DEX, or gaining an ability point at level 12), she may then use the benefits of the Mobility feat. If she has a DEX score of 13 when she reaches level 10, she may retrain the Dodge feat at level 12, provided she has maintained a DEX score of 13 throughout level 11.