You can usually defy the meta any way you like, and some excel at it (Jayce, Gangplank), some don't know where they belong (Kayle, Karma), and some, like Galio, are in a third category. He's weird because he has a nasty mage-like kit, but a tank-like ultimate, and a Kassadin-like anti-mage passive, and a support buff for teammates or himself. He's all over the place, but he works. And he's probably a favorite of mine for that reason.
|Amazing ultimate taunt||Lacks in combo|
|AP/MR sync beautifully||Semi-ignorable without ult|
|Naturally tanky||Long CD on ult|
|Great resistances buff||Lacking before 6|
|Kit is all over the place|
The Sexiest Voice
It's kind of nice that Galio, due to his rather straightforward kit, has never really needed anything to make him strong. He's never been weak, just always under the need of a few tweaks and polish. A bit more AP here, a bit of CDR there, making his taunt range match the damage range, that sort of thing. But that's Galio's strength and weakness.
I suppose when you make a champion entirely based on one concept, his whole kit is going to be lacking, but Galio's biggest advantage lies in getting that a nasty multi-hit taunt, and accordingly, the rest of his kit only gives him small advantages to doing that job. His nukes still hurt – not everyone can build tanky and gain damage from it, see also Ryze – but he's only got two of them and really all you want is to get in with that slow/gust.
So he works strongly in two positions – in lane as a counter to AP heavy champs, usually mid, and bot lane as a harass-defensive support. Both come with two distinct advantages.
As a mid mage, he can build pure resistances and shut down the enemy mage (if that's what they pick, anyway – an AD assassin will give you problems). He's popular against Le Blanc for this exact reason, as all she has is burst, and if she can't burst you, she's done. But it's not the best way, and you can just as easily run Mordekaiser or Cho'Gath and have more lategame presence beyond Galio's one mighty taunt. This is why I like to run him as support instead - you still get the taunt, you still get the tanky Galio, but you don't lose a mage.
As support, especially in season three, you naturally build tanky items anyway, such as Aegis/Runic, and support items end up falling naturally into what Galio already wants to do. CDR helps him have his ult faster (Kindlegem, Ionian), mana regen helps him harass (Philo, Mana Manipulator, Chalice of Harmony), and building durable helps him do more damage. It's one of the reasons I like an early Chalice on him, as early as you can, built into a Crucible later. Shurelia's helps him close the gap, Twin Shadows gives him AP and MR and a can't-miss slow, all syncing up towards getting his ult off.
Sadly, No Bronx or Broadway
Similar to Rammus, don't make the mistake of seeing how well he syncs up with one resistance type and building only that. As mid, you have all the farm you want, so you need to get HP (as if that wasn't obvious in the current meta) and later you will want armor. This is why the Aegis is so great for him, every stat he needs and area buff.
Support items are standard – Philo, Wardstone, build up into Shurelia's and Ruby Wardstone. But you will also want a Chalice, possibly even earlier than Philo, for spamming the hell out of your harass. Nothing is worse than a gank coming right as you're out of mana and can't gap close or use your ult. Look at what the lane is doing based on your harass, and see if it's worth it to play passive until you get a gank. Nothing beats a Galio taunt with a Lee Sin gank and a Graves burst.
Galio's summoners can drift around a bit, either Heal for support, Barrier to tank more burst, Exhaust for kill lane, but regardless of what you take otherwise, always take Flash. Trust me. Nothing beats a flash-taunt right on top of the enemy AD carry, or Katarina. This is also why some Galio players who go top or mid like to pick up Teleport. If your team wards enough, nothing sucks as bad as a Baron attempt turning into “A wild GALIO appeared! GALIO used Idol of Durand! It's super effective!”
One final note on his taunt is that it's affected by tenacity. Anytime you get into a fight where you're using it, make note of who's got Merc Treads/Zephyr/Spirit of the Ancient Golem, or worse, Quicksilver Sash/Cleanse/Mercurial Scimitar. If they're a priority target – let's say Vayne picked up a Zephyr earlier – be sure to cancel your ult early so it gets the full damage on them, because once their tenacity kicks in, they are gone, and you need that damage to go off.
Other good items for him are the Abyssal Scepter – the stats alone are great, but the passive helps immensely since most melee champs will be drawn into its range when the taunt fires off its bonus damage. And it will hurt. Rod of Ages lets him sustain if he's that tanky mid, Warmogs goes on just about anyone and everyone these days, and if you just want to hit like a gargoyle dropped from the top of Xanatos Enterprises, the Deathcap is always nice. And, because of the way Galio works, magic penetration sets him up for great synergy with Thornmail.
Even though you're gonna get focused, don't bother using his resistance buff on yourself if you're not taking any damage. When you prep for a flash-ult, sure, you'll need the tankiness and health returns to survive the whole team fighting you, but if you're just hanging in the back and an Olaf gets caught, throw it on him. It's a nice buff, and if you're low, you get healed for it. This is what you do in support lane too, if your carry starts to get focused and you're too low to help. Buff them, nuke slow and Gust to get them out, and flee.
Galio's a strong pick as he ever was, you just sacrifice quite a lot in favor of that nasty, nasty ult. But if you can pull off a couple miracle taunts onto a priority target or two, the tides completely turn, and that's why you pick him. He's a one-hit wonder, but that one hit can destroy a teamfight.