A hero that only recently first caught my genuine attention is the Blood Mage. The Blood Mage possesses an extremely versatile set of spells, that allows him to both support allied heroes, encumber enemy heroes and dish out tons of damage.
The Blood Mage's wide use makes him viable as either first, second and third pick. In this article I'll take some examples to explain how he should be used in the different strategies.
Before starting off this paragraph I'd like to convey a disclaimer. The Blood Mage is rarely seen as a first hero pick (unless you watch Angry Korea Man, that is) and this isn't without reasons, as he has some glaring weaknesses in the early game. He can't creep nearly as efficiently as the Archmage can with his Water Elementals and he is quite a bit more vulnerable to early-game harass compared to Mountain King. Therefor you want to use him in strategies, where you avoid these two things as much as possible.
Blood Mage first against Orc:
We all know that the Orc race tends to rely quite heavily on the massive damage output from Blademaster. WithBanish you can negate this damage efficiently, buying yourself time in fights and skirmishes. Banish can (on level 1) disable Blademaster for 4 seconds (or 12 seconds for non-hero units), and even longer, as Banish has no cooldown, although using it repeatedly drains your mana quite fast. Now; how do we best abuse this, then? One of the main reasons why Human rarely goes for a fast expansion against Orc, like they often do against Undead and Night Elf, is the overwhelming brute force from the Blademaster and Grunts. With the Blood Mage we can, however, work around this issue! Just watch this beautiful game from TH000 against FoCuS, where he executes Blood Mage first incredibly well:
This is one of my absolute favorite games. It's obvious that TH000 has a very well thought-out gameplan, which he executes with great success.
Blood Mage first against Human:
Another strategy with Blood Mage first is Flame Strike harass. This works best against Human as you often havea good chance of reaching level 3 without getting harassed too much - especially on maps like Terenas Stand. Another reason as to why this works well against Human is, that their peasant line is quite vulnerable, so when you can skill Flame Strike to level 2, you can navigate your Blood Mage to the enemy base and start making bonfires on top of the peasants. This strategy benefits a lot from your opponent not being on the tip of his toes, so it's hard to make it work against higher leveled players - but definitely not impossible!
The place where the Blood Mage shines the most is, obviously, when his weaknesses isn't as conspicuous. When picking Blood Mage as a compliment to another hero, you avoid said weaknesses, which is why I usually pick him as a second hero.
Blood Mage second against Human:
The Mountain King has historically seen a lot of play as a first hero against Human. Especially Sky was a big advocate of this strategy for a period of time in Human mirror. When going Mountain King first, Blood Mage is an obvious candidate for a second hero, as the two work extremely well together. One of the Mountain King's biggest weaknesses is that he runs out of mana easily. Siphon Mana allows you to keep your Mountain King replenished with mana throughout the game, which is a huge deal.
Another reason why they complement each other is Banish. Banish amplifies spell damage taken by 66%. With Storm Bolt being the highest damaging single-target spell in the game, this is very significant (Level 3 Storm Bolt deals 350 damage without Banish and 581 with Banish).
Blood Mage second against Orc:
The spot where I recently have found a lot of joy in Blood Mage is against Orc. Even though Beastmaster or Mountain King are picked as a second hero by the vast majority of Human players against Orc, I think there is a serious case to be made in favour of Blood Mage for this spot.
He can't cancel the Orc's t2 buildings or preassure burrows as well as a Beastmaster can, and he's more vulnerable than Mountain King, but, if played right, Siphon Mana can be absolutely devastating for the Orc. With both Brilliance Aura and Blood Mage, you are almost guaranteed that you can keep spamming Water Elementals with Archmage.
We've all experienced a Shadow Hunter which keeps healing the already beefy Orc army, making it seemingly invincible. With Siphon Mana you can put an end to this, by draining Shadow Hunter's mana pool empty. Siphon Mana is not even exclusively effective against Shadow Hunter, but is also great on Blademaster to prevent Wind Walk or even Spirit Walkers to prevent them from disenchanting your Sorceresses' slow.
This game might, at first glance, look like a bad example of why Blood Mage is good, as Cash manages to kill him quite fast, but he managed to do three very important things, that had a large impact on the game:
Even though I have a substantial predilection for Alchemist, I must admit that Blood Mage, in my opinion, takes the cake when looking from a pure game-play perspective. His flexibility and extremely low cooldowns always makes him feel like a centerpiece in your army. He requires a lot of attention when you micro in team fights, but the effort you put into it, almost always seems to pay off.