Vamana is a very aggressive and tanky God, if you want a more passive tank, do not play Vamana. He suffers in the beginning due to mana limits, but it doesn't take long to over come.
Quick note, only on the second build will I have a set time for getting an ability item. Other than that buy them as needed.
He is very hard to kill
He can be built different (and viable) ways
His abilities are easy to use
He can run away from enemies/out of tower range faster than most.
He can chase down enemies better than most.
He can knock enemies into the air.
His ultimate allows him to tank a tower/phoenix/Minotaur
Built pure tank he can tank tower/phoenix/Minotaur
Built with my pure damage build he can solo Minotaur
Does very little damage to other gods if built pure tank (expected)
Is very slow damage dealer until a few points are put into his Armored Umbrella
More often than not, people will ignore you in team fights, making it hard to protect your team.
Sleeping Giant (Passive)
When he is not in Colossal form, damage taken from enemy Gods will decrease the cooldown of his ultimate by 1sec. When in Colossal form, damage from enemy Gods will increase the duration by .5secs, up to a max of 10secs. 15% of Vamana's Physical protection is converted to Physical Power.
Clear the Path
Vamana opens his umbrella charging forward doing 70/110/150/190/230 (+40% of your physical power) physical damage and knocking up any enemies hit. Costs 70/75/80/85/90 mana, 15sec cooldown.
Does 85/140/195/250/305 (+100% of your physical power) physical damage to all enemies in a cone. Costs 60/70/80/90/100 mana, 51/14/13/12/11sec cooldown.
Vamana throws his umbrella forward hitting everyone in its path for 50/85/120/155/190 (+20% of your physical power) physical damage and slowing enemy attack speed and movement speed by 25% for 3sec. The umbrella will return to Vamana and will hit everything in the path. Costs 60/70/80/90/100 mana, 13sec cooldown.
Vamana grows into a giant for 6secs (modified by passive, see above). He gains 5/10/15/20/25 physical/magical protection, 35/55/75/95/115 physical power and regens 5% of his max health every second. In addition his basic attack is an aoe. Costs 100 mana, 90sec cooldown.
Start off by buying basic rank Reinforced Boots, Breastplate of Valor, and 2 Health Potions.
Finish off the Reinforced Boots reinforced boots and the Breastplate of Valor , the early defense will make it hard for people to push your tower.
The next item is the Gauntlet of Thebes , mainly because it builds stacks (1 per minion, 5 for God) per kill and needs to be built up as early as possible.
After that the Voidblade will not only add damage and protection, but will lower enemies physical defense.
The next item is the Stone of Gaia this will stop casters from dealing damage as well as give more health and mana regen.
The last item is Devourer's Gloves devourer's gloves, at this point you have so much defense that stacking more is pointless. This item will give stacks per kill (they will be removed if you die) and since you are hard to kill (and if you play right pretty much impossible to kill) you will be able to keep the item maxed. This boosts your attack damage and lifesteal, the jungle and minion waves will now let you heal yourself in a very quickly after a teamfight and still let you push forward.
Start off by buying buying the basic rank of Reinforced boots, hand of the gods and two health potions. Grab blue buff before heading to lane.
Finish off the Reinforced Boots reinforced boots and then buy the Hide of the Nemean Lion . The Hide of the Nemean Lion will reflect 25% damage back from basic attacks and boosts health and physical defense.
After that you will want the Golden Bow golden bow, this item will add a 50% damage aoe to your basic attack, a small chance for critical hits, and a minor speed boost. This will do two things, one it will let you destroy minion lanes/jungle. Two if you are fighting in a mob of enemies it guarantees that your target is being hit with at least 50% of the damage.
Next item is Devourer's Gloves Devourer's Gloves, the lifesteal and physical damage from this item at max stacks are amazing. If you are dying a lot you may want to switch to a different lifesteal item, Soul Eater being the best.
After that Deathbringer will be the next item. It has physical power, critical chance and critical damage. This item will greatly boost your ability to kill and make your enemies fear getting close.
The final item is Titan's Bane , this has some physical power, but mainly it has a 45% physical penetration. anyone fighting you will most likely have armor at this point (unless they fail to understand how armor works), this will eat through just under half of it.
The ultimate is less useful in this build, as using your other abilities will deal more damage. However your ult will still let you tank towers and the like and is still a great ability to use to run away when you are almost dead since the life regen is crazy.
Start off buying Reinforced Boots, Jotunn's Wrath and a Health Potion. If you want to be more tanky build a Breastplate of Valor breatplate of valor instead, the main reason for the Jotunn's Wrath is the 20% cooldown reduction. I prefer the Jotunn's Wrath for the mana and physical power.
Build up your Reinforced boots reinforced boots and which every item above you picked up.
After that build a Hide of the Nemean Lion , this is a great tank item as it also reflects basic attack damage back.
The next item is the Stone of Gaia , this will be your magic defense item and will also regen your life and mana.
With your defense items out of the way it is time to switch to your aggressive items starting with the Golden Bow Golden Bow. This will add aoe to your basic attacks, increase your critical chance, and give you a small speed boost.
The last item to buy is the Deathbringer [icon=death bringer size=55, this item adds physical power, critical chance, and critical damage.
You will lack armor pen, but at the same time you will have strong defenses. This is the better build for being useful in team fights.
If you can, get blue buff every time it spawns. Armored Umbrella
will deal a lot of damage when killing jungle camps.
When in lane, try to use your Umbrellarang when the minions are charging down the lane, you should be able to hit each of them twice doing this. Follow up with a Armored Umbrella will kill most of the mobs.
Armored Umbrella is your best attack, and thus it is your best bet for clearing out waves of minions.
Use your Umbrellarang to hit ranged targets and try to hit as many as you can with your Armored Umbrella since it is your best damaging attack. For build 1 and 3 you will pretty much want to start all team fights, but do not let yourself be killed. For build 2 you want to go in as a team, you lack the defense of the other two builds, but are still fairly defensive, not to mention your ultimate makes it hard for people to kill you without the help of a tower/phoenix/Minotaur. Using your Clear the Path in the middle of a fight can be useful if the enemies are grouped up, but it should be saved for knocking up Gods that have run out of the fight so you/your teammates can kill them. Your ultimate makes you the best person to tank a tower/phoenix/Minotaur when no minions or present, you want to kill the tower while the enemy is there, or you want to have a team fight on an enemy tower.
There isn't really a God that compliments Vamana or shuts him down easily.
The only thing to avoid is laning with another tank.
Between his ability to run using his Clear the Path and his ultimate he is a very hard God to kill. It will generally take a combination of Gods or really bad timing with his Clear the Path to be shut down. Your biggest enemy is really just being over confident and getting stuck with no way out or on a tower.