Reveillark combo - With Karmic, Eternal, and Phyrexian Altar you pretty much recast everything from your graveyard again, again, and again... Havengul Lich - can pretty much steal any creature from any graveyard in 5 colors. Avenger of Zendikar - pretty much swarm with tokens. Triumph of the Hordes finishes people off. Jin-Gitaxias, Core Augur - If he could be cheated in via graveyard, your opponents better still have removal or else its game over. Seize the Day - extra attack phase could be a finisher for Horde or any army.
After a little playtesting, I made some revisions:
REMOVED Dralnu, Lich Lord - Yo I heard you like flashback so I gave your flashback spells more flashback. Sorry, you're out.
REMOVED Creeping Renaissance - not many permanents to bring back
REMOVED Decree of Pain - Too expensive
REMOVED Desperate Ravings - Not too desperate for this
REMOVED Green Sun's Zenith - Probably will regret removing this but didn't have many targets besides Prime time/Avenger
REMOVED Sylvan Library - Didn't fit flashbacking theme that Secrets did.
REMOVED Phyrexian Metamorph - Felt kind of bad removing it. Will revisit Mr. Morph.
REMOVED Doubling Season - One of the last to get cut
REMOVED Increasing Savagery - Like an aura, can be 2 for 1ed
REMOVED Trickbind - One-time temporary answer feels kind of bad.
REMOVED Past in Flames - Don't need more Flashbacking my flashbacks.
REMOVED Altar of the Lost - Too narrow.
REMOVED Sylvan Might - Needed a more global finisher...
REMOVED Mind Stone - Not helpful in 5C
REMOVED Crush of Wurms - Too expensive
REMOVED Forgotten Ancient - Too slow/doesn't fit theme
REMOVED Helm of Awakening - Too group huggin
REMOVED Praetor's Counsel - Win more sometimes.
REMOVED Jin-Gitaxias, Core Augur - Too expensive most of the time
REMOVED Shattered Perception - Never used it
REMOVED Prismatic Omen - Have enough duals/fetches now to not need color fix.
REMOVED Rites of Flourishing - Too group huggish
REMOVED Triumph of the Hordes - Never used it or not enough creature to take advantage
ADDED Bazaar of Baghdad - virtual card advantage/ "dredger"
ADDED Rout - Allows instant speed wrath, a little cheaper than decree.
ADDED Secrets of the Dead - More card draw
ADDED Cultivate - Ramp
ADDED Putrefy - Versatile instant spot removal
ADDED Spitting Image - Has "flashback" and bascially takes metamorph's spot.
ADDED Krosan Grip - Split-second needed
ADDED Devil's Play - Finisher/spot removal
ADDED Worm Harvest - Excellent chump block/token army. "Flashback" multiple times.
ADDED Mirari's Wake - Mana doubler
ADDED Terravore - Becomes big trampling fatty that synergies with Retrace/discard spells
ADDED Knight of the Reliquary - Prime Time #2 in regards to function.
ADDED Compulsion - Card filtering/looting
There's also a sub-theme of tokens that was accidentally put in or was my mind subconsiously making me play tokens again?
Also,Horde of Notions can recur Elementals from the graveyard including Crib Swap for multiple creature exiling.
I would take any suggestions as this is more casual than competitive even though the mana base is a tad expensive.
So far Flashback/Retrace count is 19 spells.
1 Galvanoth
1 Knight of the Reliquary
1 Phyrexian Metamorph
1 Primeval Titan
1 Riku of Two Reflections
1 Scavenging Ooze
1 Snapcaster Mage
1 Terravore
Recursion: (9)
1 Charmbreaker Devils
1 Dread Return
1 Eternal Witness
1 Havengul Lich
1 Karmic Guide
1 Mystic Retrieval
1 Praetor's Counsel
1 Reveillark
1 Unburial Rites
Mana ramping/cost reducers: (9)
1 Catalyst Stone
1 Cloud Key
1 Cultivate
1 Darksteel Ingot
1 Mirari's Wake
1 Oracle of Mul Daya
1 Phyrexian Altar
1 Sol Ring
1 Wood Elves
Card Drawing/Tutors: (14)
1 Compulsion
1 Consecrated Sphinx
1 Deep Analysis
1 Demonic Tutor
1 Increasing Ambition
1 Faithless Looting
1 Forbidden Alchemy
1 Mulldrifter
1 Mystical Teachings
1 Quiet Speculation
1 Secrets of the Dead
1 Shattered Perception
1 Sphinx of Uthuun
1 Visions of Beyond
1 Beast Within
1 Crib Swap
1 Chainer's Edict
1 Devil's Play
1 Divine Reckoning
1 Hallowed Burial
1 Krosan Grip
1 Putrefy
1 Ray of Distortion
1 Rout
1 Sever the Bloodline
Token Makers: (4)
1 Avenger of Zendikar
1 Cackling Counterpart
1 Grizzly Fate
1 Increasing Devotion
Other Spells: (5)
1 Increasing Vengeance
1 Fires of Yavimaya
1 Seize the Day
1 Spitting Image
1 Worm Harvest
Lands: (39)
1 Bazaar of Baghdad
4 Forest
2 Island
2 Swamp
1 Plains
1 Mountain
1 Bayou
1 Savannah
1 Stomping Ground
1 Tropical Island
1 Taiga
1 Plateau
1 Volcanic Island
1 Temple Garden
1 Underground Sea
1 Badlands
1 Scrubland
1 Misty Rainforest
1 Flooded Strand
1 Marsh Flats
1 Windswept Heath
1 Verdant Catacombs
1 Arid Mesa
1 Woodland Cemetery
1 Command Tower
1 Rupture Spire
1 City of Brass
1 Reliquary Tower
1 Tundra
1 Breeding Pool
1 Riftstone Portal
1 Mystifying Maze
Possible game-enders:
Reveillark combo - With Karmic, Eternal, and Phyrexian Altar you pretty much recast everything from your graveyard again, again, and again...
Havengul Lich - can pretty much steal any creature from any graveyard in 5 colors.
Avenger of Zendikar - pretty much swarm with tokens. Triumph of the Hordes finishes people off.
Jin-Gitaxias, Core Augur - If he could be cheated in via graveyard, your opponents better still have removal or else its game over.
Seize the Day - extra attack phase could be a finisher for Horde or any army.
REMOVED Dralnu, Lich Lord - Yo I heard you like flashback so I gave your flashback spells more flashback. Sorry, you're out.
REMOVED Creeping Renaissance - not many permanents to bring back
REMOVED Decree of Pain - Too expensive
REMOVED Desperate Ravings - Not too desperate for this
REMOVED Green Sun's Zenith - Probably will regret removing this but didn't have many targets besides Prime time/Avenger
REMOVED Sylvan Library - Didn't fit flashbacking theme that Secrets did.
REMOVED Phyrexian Metamorph - Felt kind of bad removing it. Will revisit Mr. Morph.
REMOVED Doubling Season - One of the last to get cut
REMOVED Increasing Savagery - Like an aura, can be 2 for 1ed
REMOVED Trickbind - One-time temporary answer feels kind of bad.
REMOVED Past in Flames - Don't need more Flashbacking my flashbacks.
REMOVED Altar of the Lost - Too narrow.
REMOVED Sylvan Might - Needed a more global finisher...
REMOVED Mind Stone - Not helpful in 5C
REMOVED Crush of Wurms - Too expensive
REMOVED Forgotten Ancient - Too slow/doesn't fit theme
REMOVED Helm of Awakening - Too group huggin
REMOVED Praetor's Counsel - Win more sometimes.
REMOVED Jin-Gitaxias, Core Augur - Too expensive most of the time
REMOVED Shattered Perception - Never used it
REMOVED Prismatic Omen - Have enough duals/fetches now to not need color fix.
REMOVED Rites of Flourishing - Too group huggish
REMOVED Triumph of the Hordes - Never used it or not enough creature to take advantage
ADDED Bazaar of Baghdad - virtual card advantage/ "dredger"
ADDED Rout - Allows instant speed wrath, a little cheaper than decree.
ADDED Secrets of the Dead - More card draw
ADDED Cultivate - Ramp
ADDED Putrefy - Versatile instant spot removal
ADDED Spitting Image - Has "flashback" and bascially takes metamorph's spot.
ADDED Krosan Grip - Split-second needed
ADDED Devil's Play - Finisher/spot removal
ADDED Worm Harvest - Excellent chump block/token army. "Flashback" multiple times.
ADDED Mirari's Wake - Mana doubler
ADDED Terravore - Becomes big trampling fatty that synergies with Retrace/discard spells
ADDED Knight of the Reliquary - Prime Time #2 in regards to function.
ADDED Compulsion - Card filtering/looting