So do you guys remember when we had the Black Market Brawler minigame, for the Bilgewater Event, and it had some pretty cool items.  So far Dead Man's Plate is the only Black Market item that remains in the main game, the rest are pretty much long gone unfortunately.  But I think it would be cool to have some of the Black Market items to return to the game for the highly anticipated, Mid-Year Mage Update!  The reason why they should be re-added is because these items provide everything an AP Mage would need:Mana regen, CDR, AP, and even mobility!

Here is the list of what should be added for the MYMU:  

Rite of Ruin item
Rite of Ruin is an item that costs 3000 [1] and 765 [2] if its components, Lost Chapter and Amplifying Tone, are already bought.  This item provides 100% base mana regeneration, 100 ability power, 20% cooldown reduction, and has a unique passive called Razing which allows the buyer to gain charges upon moving or killing enemies, up to 300 charges. Attacking structures expends 50 charges to deal 100 (+15% AP) bonus true damage.  This item is made for mages who can push lane like Ziggs and Xerath and also you don't have to go back to fountain and waste gold on an elixir. 

Staff of Flowing Water is an item that costs 1635 [3]and 300 [4]if its components, Chalice of Harmony and
Staff of Flowing Water item
Amplifying Tone, are already bought. This item provides the buyer with 25 magic resistance, 50% base mana regeneration, 40 ability power.  Because it builds from Chalice, every 5 seconds, 2% of the buyer's missing mana will be restored.  It has a unique passive that grants 30% movement speed and 10 flat mana regeneration while in the river.  This is an item made for roaming midlaners because of the movement speed and mana regen it gives whenever at rivir.

Netherstride Grimoire item

Netherside Grimoire costs 3000 [5]and 765 [6]   if its components, Lost Chapter and Amplifying Tone, are already bought. Netherside provides the buyer with 100% base mana regeneration, 100 ability power, and 20% cooldown reduction.  Netherside has a unique passive that grants the buyer 20% movement speed for 2 seconds whenever you deal ability damage.  If this item were to return, it would be indirect buff to champions like Brand and Cassiopeia because Brand's passive and Cassiopeia's poison will proc the movement speed passive and this will solve their biggest weakness, 'immobility.'

Pox Arcana costs 3000 [7] and 765 [8] if it's components, Lost Chapter and Amplifying Tone are already purchased.  
Pox Arcana item
Pox Arcana has the same stats like Netherside and Rite of Ruin, but has a very interesting passive that differs from the other items.  It's passive is called Disease Harvest,which deals 100 magic damage plus 20 (+5% AP) per stack of Pox (maximum of 200 (+25% AP)) to all nearby enemies affected by Pox, and restores 5% of your maximum mana for every Pox stack harvested. 60 second cooldown.  DoT mages like Malzahar and Swain could use this kind of item.

Lost Chapter item

Last but not least, Lost Chapter, which is an item that costs 1800 [9] and 380 [10]if Fiendish Codex and Forbidden Idol are already purchased. Lost Chapter provides the buyer 100% base mana regeneration and 50 ability power. It's Unique passive grants 20% CDR.  Now I know what you're all thinking, it's a Morellonomicon clone with less ability power, but it can be built into stronger items like Rite of Ruin, Netherside, and Pox.