Last Update: April 2011
Reasons for high Arcana
The Sage of the Ages epic destiny utility power allows for some very very beautiful things, assuming you get your arcana check high enough:
Trick of Knowledge (Utility 26)
Encounter * Arcane
Minor Action * Personal
Effect: Make an arcana check and gain a benefit based on your check result until the end of the encounter.
30 or lower: no effect
31-35: +5 to saving throws
36-40: +2 bonus to all defenses
41-45: +2 to arcane attack rolls
46-50: make saves at the beginning of your turn instead of end.
51-55: pick 2 of the below benefits
56-60: pick 3
61 or higher: pick 4
... in other words, with good optimization you will get +5 to saves, +2 to all defenses, +2 to attacks, and save at the start of your turn.
Other benefits of high Arcana
Sorcerous Vision (feat, AP): Use Arcana check for Insight and Perception checks (requires Sorcerer class or MC Sorcerer)
Suggestion (free mage utility power, HotfL): Use Arcana instead of Diplomacy
Arcane Mutterings (lvl2 encounter skill power, dragon 379): Use Arcana instead of Bluff, Intimidate or Diplomacy check
Fools Gold (lvl2 ritual, AP): Create illusionary gold, worth x100 component cost. DC to find out: your arcana check. 10 gp -> 1000gp :D
Seek Rumor (lvl2 ritual, FRPG): Substitute Streetwise with Arcana to find out everything there is to know...
Knock (lvl2 ritual, PHB): Arcana+5 instead of Thievery to open locks
Mythic Senses feat (PH3, requires Minotaur) - use Perception checks in place of initiative checks - combine with sorcerous vision -> arcana for initiative
Cunning Artifice (Dragon 387, requires Artificer, Changeling) - use Arcana for Bluff in changeling racial power
Autohypnosis (heroic feat, Psionic Power): Use Arcana for Endurance Checks if not bloodied
Arcane Trickster (PP): Use Arcana for Athletics Checks
How to get it
iron of spite (head, phb) +6 item bonus
runic armor (armor, av2) +6 item bonus
ring of wizardry (ring, phb) +3 item bonus
mirror of secrets (Artifact, Open Grave) +2/+4/+6 item bonus (concordance dependent)
opal ring of remembrance (ring, AV): +4 item bonus
staff of psicraft(staff, phb3): +1/+2/+3 item bonus
skill focus (phb) +3 feat bonus
highborn drow (Dragon 364, requires drow) +2 feat bonus
power of arcana (Divine Power, domain) +2 feat bonus
yuirwood feyfriend (Dragon 370) +1 feat bonus
bardic knowledge (phb2) +2 feat bonus
Drowning of Nhalloth (Dragon 391, requires Shadar Kai) +2 feat bonus
Inspire Competence +2 power (Bard encounter or Wand of Aptitude daily power)
Good Omens (Cleric PP Divine Oracle daily util, phb): +5 power bonus
Fevered Certainty of Caiphon (warlock daily util, dragon 366): +5 power bonus
Elexir of Aptitude (consumable, AV): +1/+3/+5 to skill check, lasts 1 hour, requires healing surge
Symbol of Excellence (holy symbol, AV): +1-6 power bonus, requires daily item use
CD: Ancestral Guidance is a power bonus of +Wisdom for one check. Requires Spirits of the Past.
CD: Divine Excellence is +2 power to you, and grants a +2 power on the same skill to you and all allies until the end of your next turn. Requires skill domain.
Eldarin (phb) +2 to int, +2 to arcana
Gnome (phb2) +2 to int, +2 to arcana
Deva (phb2): +2 to int, Memory of a Thousand Lifetimes -> reroll with +1d6 bonus (+1d8 with feat)
Shardmind (phb3): +2 to int, +2 to arcana
Changeling (eberron) + feat: becomer (dragon 386): +2 int, +2 to arcana
+2 (generic, phb2)
High Imaskar (FRPG): reroll arcana check, keep second result
Netheril (FRPG) +1
The Great Dale (FRPG) +1
Paragon of Learning (ED Sage of Ages feature, AP) +6 untyped
Arcane Underpinning (PP Academy Master feature, dragon 374) +2 untyped
Dabbler (PP Jack-of-all-Trades feature, MP2) +2 untyped
Unseen Aid (Sorcerer encounter util, PHB2) +2 untyped
Mage class (for free, at level 21) +3 untyped
Disciple of Lore (heroic feat, HotFL) +1 untyped to all trained skills
Talent Shard (Consumable, minor action, PHB3) +1 to +6 untyped
Resourceful Action (Halfling PP Halfling Scoundrel feature, PHB2) +5 untyped, requires AP
Fate of the Void (Star Pact Warlock pact boon, PHB) +1 untyped/ enemy killed
Morans Eye (P1 King of the Trollhaunt Warrens, wonderous item/implement, probably unique) +5 untyped for posession
Moonstone Sphere (E1 Deaths Reach, wonderous item/implement, probably unique) +2 untyped for posession
Head of Vyrellis (H3 Pyramid of Shadows, wonderous item/implement, probably unique) +2 untyped for posession
Tacticans Armor (Armor, AV): +1 untyped (maybe, check wording with DM)Familiar: Book imp +2 (Dragon 374)
Familiar: Crafter Homunculus +2 (Dragon 374)
Familiar: Rakshasa Claw +2 (Dragon 374, paragon) + free action item stow/retrieve (could allow to switch head slot items?)
Familiar: Skull +2 (Dragon 374)
Familiar: Greyspawn Shortfang +2 (paragon) (Dragon 374)
Familiar: Blazing Skull +2 (epic) (Dragon 374)
Familiar: Chaos Shard +2 (epic) (Dragon 374)
Familiar: Coure Attendant +2 (Dragon 290)
Relics of Creation (AV2, epic item set): +2 to +6 (depending on # of setitems)
Bonuses granted by Allies
Aid Another: +2 untyped per character helping BUT: requires standard action -> not practical
Clockwork Precision (Bard daily util, AP): aid another adds +3 untyped per character helping, but still requires standard action -> not practical
Find Another Way (Bard PP Lifesinger feature, AP) : +2 untyped for allies within 5 squares
Speak with Spirits (Shaman Class Feature, phb2) + feat Spirit Speaker: +wis bonus to skill check
Crucial Advice (Ranger Util 2, phb, encounter, immediate reaction): reroll check, with +wis power bonus, but works only on allies (not oneself)
Fatesinger Bard: Majestic Word -> roll twice, use better result
Glittergold's Gambit (Channel Divinity feat, FRPG) -> reroll attack roll or skill check
Golden Mean (Lord of Fate ED daily utility power, AP): take 10 on any check
CD: Sune's Touch is for an ally. One ally in Close Burst 1 gets +2 power to his next skill check until the end of his next turn.
Potion of Clarity (consumable, AV, costs healing surge): reroll with +1 to +6 bonus
Arcane Insight (Wizard Util 2, Dragon 366, encounter, free action): reroll arcana check, use better result
Keeper's Prescience (Sage of the Ages 24 ability): roll d20 each round, switch result with any roll during that round
Dark One's Own Luck (Warlock Daily Util 6, PHB): reroll an attack roll, skill check, ability check, or saving throw
Kensei Control Action (Fighter PP Kensei feature, PHB): AP->reroll attack roll, damage roll, skill check or ability check (no extra action)
CD: Divine Fate is Revenant-only, but not tied to a deity and gives a RtB on any skill check.
CD: Imminent Luck is GOOD. If you spend a power to reroll, and the reroll is lower, you can expend CD: ID not to expend the power. Requires only the luck domain. Note that this works with RtB powers.
Bonus to specific Arcana Checks
Note: These bonuses won't work with Trick of Knowledge. But they might still be of interest to get a high arcana result in other circumstances...
Consult Mystic Sages (ritual, skill:religion): Get +10 to an arcana check (specific purposes given in a list)
Arcane Ritualist (feat, AP): Get a untyped +2 bonus for one specific ritual
Foreign Memories (feat, Dragon 389): +5 feat bonus, only related to aberrant creatures
Oghmas Recall (feat/channel divinity power, FRPG): Get a +10 power bonus for a knowledge check
CD: Aureon's Instruction is RtB (reroll take better) with knowledge or monster knowledge checks until the end of your next turn. Requires Aureon.
CD: Sure Knowledge is RtB for a knowledge check. Candidate for an ally feat, as it's you or an ally.
Historical Revelation (enc. Skill Power): ally can reroll knowledge check
Let your Familiar also make the check: especially useful for knowledge checks (since they are free actions)
15(lvl)+9(int)+6(item)+5(trained)+2(race)+2(background)+6(ED)+2(familiar)+2(PP)+3(feat)+6(items of creation)+6(talent shard) = +64
Which would allow us to always roll 65 for all 4 benefits. Or roll Insight/Perception/Bluff/Intimidate/Diplomacy/Streetwise/Thievery/Endurance/Athletics +65. And Initiative +65. And your fools gold will be more real than normal gold . But more versality is always better, since you usually don't want to optimize arcana only, more ways to get there or even higher are welcome...