Currently, there are only 2 items in the game that can be used for mana-draining enemy DG's: Warlord's Punisher and Guantlets of Despair. Both received slight buffs in update 1.19 - but it could be argued that both are still underpowered and relatively useless, compared to other items of similar cost.
I would love to have mana-drain be a viable build for certain DG's, esp. Reg and TB.
The thing is, I don't think that either item needs much to make them useful items. Here are the current stats on the Punisher:
Warlord's Punisher (trinket)
Cost: 2250 (reduce to 1750)
1 sec cast, 30 sec cooldown, 15 yard range (increase to 30 yards)
300 damage to target, which arcs to nearby enemies
DG's lose 400 mana (increase to 500 mana)
+30 weapon damage (remove this effect - not thematically necessary)
On the face of it, this looks decent. But in practice, it just doesn't work. The biggest issues, in my mind, are COST and RANGE. If you reduced the cost of this item to 1750 (so it's competing with items like Wand of Speed and Vlemish Helm), and increased its range to 30 yards, you'd have an item that many players would pick up. I've tried using the Punisher in a variety of builds and the biggest issue I have is that I'd like to be able to use it from a medium distance - 15 yards is actually pretty close to an enemy DG. If you could take 500 mana away from an enemy DG that was level 3 or so (when you could afford a 1750 item), that could be pretty devasting to certain builds. It could be particularly effective against the infamous Erebus-general build that is mana-reliant: the mana loss means less Bite and Swarm, and the damage could theoretically kill his entire minion army. Nice!
Guantlet's of Despair (Gloves)
Cost: 1750 (increase to 2000)
+350 mana (increase to 500)
15% chance to drain 200 mana (increase to 20% chance and make this an actual drain)
The Guantlets would be a good item, if they actually drained mana. From what I've seen, they cause an enemy DG to lose mana, but you don't actually get any mana yourself. These should provide the equivalent of life-steal, but in mana. If I'm wrong about this, please let me know.
[EDIT] Checked the lua files. I'm no expert in reading these, but this is what I see for the G of Despair:
---------------------------------------------
Name = 'Item_Glove_030_Drain',
BuffType = 'ITEM_GLOVE_030_DRAIN',
Debuff = true,
CanBeDispelled = true,
Stacks = 'REPLACE',
Duration = 0,
Affects = {
Energy = {Add = -200},
},
Effects = 'Manadrain01',
EffectsBone = -2,
---------------------------------------------
Nothing about the using player gaining any mana, I don't think. Anyone know how you'd fix the code to address this?