Basics (how to)
You need to be “at cap” and have a heart of wood and go to the reincarnation grove in the hall of heroes.
There are 2 different at caps and many different hearts. Heroic cap is level 20. Cap is 30. The type of heart needed depends on your current race not the one you are going to.
If you are at heroic cap on a non-iconic race, you can heroic TR using a heroic true heart of wood obtained in the twelve from the lava guy for 20 tokens of the twelve. You can then start at 1 as a standard race or 15 as an iconic. You will get a past life for the class you have the most levels in (there is a complicated relationship for multiclasses with equal levels. see wiki).
You also have the option of using a heart of blood also found in the twelve for tokens to do a racial TR, it is the same as a heroic TR but gives a past life based on race not class.
A popular place to get tokens to trade for hearts is running Devil Assault on epic normal as it has two chests with a chance to award a full token. Another method for fast tokens of the twelve is running cannith challenges and trading ingredients for tokens.
If you are at cap on an iconic, you can iconic TR using an iconic true heart of wood obtained from heart seeds/comms of valor (cov). You can then start at 1 as a standard race or 15 as an iconic. You will get a past life for the class you have the most levels in. You will also get an iconic past life for your current race.
If you are at cap with 6mil karma in an Epic Destiny (ED) sphere (you DO NOT lose any ED progress), you can do an epic reincarnation using an epic heart of wood obtained from heart seeds/cov. You choose from the available epic pasts in a max karma sphere. If you do this on an Iconic you will have to level to cap again. If you do this on a non-iconic you can do a heroic/racial TR or level to cap. This is a lesser reincarnation that returns you to 20 with a full rebuild of stats and feats (class, race, alignment not changed), and gives you an epic past life feat.
Active and passive Past life feats: (why to)
Iconic and epic pasts give active (stance) and passive feats. You can have one active stance in use per sphere and one iconic, for a total of 5 stances. It’s best to knock out 3 of one past life in each sphere first, rather than one of each in a sphere to get max effect from the stance.
Heroic or class past lives give a passive (free) feat and access to a purchased feat.
Racial past lives give skills, stats, and racial action points.
Epic: Epic completionist requires 3 each from the following four spheres and grants a 4th twist of fate slot, you also get 1 twist point per 4 past lives. There are 3 epic past lives in each of the four spheres. The passive for each sphere stacks up to 9 times, (3 times from each past life). The stance stacks 3 times.
Passive: 2ac+1ac/10levels. All 9 stacks makes you untouchable for much of heroic levels.
Stances: skill mastery +1 all skills, doublestrike +3, fortification +10.
Usefulness: Skills is nice to get that little bit of UMD or swap for trapping, DS is a must for any melee, Fortification is really nice at low levels before your gear can get to 100%.
Passive: 3hp + 4hp/10levels. Huge boost of hp with 9 stacks. 3barb + 9 primal will have you around 100hp at level 1.
Stances: Doubleshot +3, fast healing heals 5hp+5hp/5levels each minute, colors of the queen is a shiradi rainbow proc on a long cooldown.
Usefulness: For ranged, DS is a no brainer. Colors can be fun when you get a sunburst at low levels or demon poison on a boss, but very unreliable. I run fast healing almost always. UPDATE: in reaper fast heal doesn’t perform so I’m back to running colors.
Passive: +3 prr. 9×3= 27 Nice boost in prr for anyone. Great for light armor/robes due to lower base prr.
Stances: Brace +1 saves, Power over life and death +10 pos/neg spell power, block energy 10% elemental absorb when blocking.
Usefulness: With heal amp and high spell power the positive is not needed, would be nice on a pm though. Block energy does not require a shield, but unless you are quick to block it’s not very useful. I run brace always, but you could run life/death for a little extra healing when casting spells.
Passive: 1% elemental absorb. Every little bit helps. (Wish mrr had been around when this was made, would likely be 3per like divine is for prr.)
Stances: energy criticals +3% crit chance with elem and sonic, enchant weapon +1 to weapon enchantment, arcane alacrity spell cooldown reduced.
Usefulness: For any non caster enchant weapon is only option and it’s nice, especially at low levels (note: breaks celestia light type just like swashbuckler). For a nuker: crits, for a DC caster: alacrity.
Iconic (not part of epic completionist)
Passives: SDK: dodge is nice any light armor/robe user. PDK: prr which is always good. ML: devotion spell power which helps fleshies but it’s pretty small. BF: extra fort is nice when low level but high level gear covers it. GN: more mmr is good. AS: fort save.
Actives: I typically run SDK iconic stance unless noted below. PDK is odd as it’s a run speed/saves action boost that puts other iconic stances on cooldown. ML stance is nice for light nukers and I run it on my warlock with utterdark. BF past is only useful if you are BF/WF. DG: is great for illusion spells, might also run it on a G-O-O warlock for spellpower. AS: is a must for TWF.
Heroic freebies tend to be good and purchased lame.
Purchased feats: mostly useless except for wiz past (+1 to all DC, with 10 charge magic missile clickie) on a DC caster and completionist (+2 to all stats and skills). Bard is arguable for an enchantment build (+1 enchant DC). Monk for unarmed (+1/2(w) unarmed).
Passives:stacks 3 times
Artificer: +1 int skills and umd. Great for trappers or umd users (should be everyone).
Barbarian: 10hp. Nice but not as big a % of total hps as it used to be
Bard: +2 enchantment saves (not dc) and a song if you have songs. Meh, songs only if you are a bard/fatesinger, most enchant saves are covered by gear, but it’s better than nothing.
Cleric: better turn undead and +1 conj dc. Good for an undead spec’d cleric. It does boost web/tentacle DCs also.
Druid: hirelings/summons/pets/charmed get +2 to all stats. Sounds great but mostly useless except for low level and some stat checks (tear/xorian/partycrashers).
Favored Soul: +20 spell points and +1 spell pen. Anyone can use more sp (for EDs), spell pen is great for a DC caster.
Fighter: +1 atk and tactics DC. A must have for a tactics specialist.
Monk: +1 damage. Nice for non-casters.
Paladin: 10 heal amp. Always nice to have.
Ranger: +2 to all elemental resists and+ 2 to ranged (non-thrower) damage. Excellent for bow and xbow users.
Rogue: +2 to trap saves, +1 SA damage. Trap saves nice, damage is lame when compare to monk.
Sorcerer: +1 evoc DC, +20 spell points. Anyone can use more sp, evoc DC great for sorc, warlock, and quake druid.
Warlock: +3 mrr. Always nice, only negative is it might be capped on a robe/outfit user.
Wizard: +2 spell pen. and wand dc. Wand dc…lol. +2 spell pen is very nice for DC caster.
Racial: The first in a race awards a skill, the second in the same race awards a stat, the third awards a racial action point. Three times all awards racial completionist free (same effects as heroic completionist). Racial past life stats do not count for feat prereqs.
Assimar: heal, wisdom
Dragonborn: spellcraft, charisma
Drow: search, intelligence
Dwarf: balance, constitution
Elf: spot, dexterity
Gnome: UMD, intelligence
Halfling: move silently, dexterity
Half-Elf: diplomacy, charisma
Half-Orc: intimidate, strength
Human: haggle, wisdom
Warforged: repair, constitution