I would say that Swain is a pretty easy charac6ter when you have learned his trick. The difficult part of things is to hit you E. With the right movement and timing, this won't be a problem.
What you do is to hit the E, then you pull them towards you, before you do that, make sure your W will hit them when you have pulled them, and the go for the Q. If you believe it is necessary, or you dive a tower, then make sure to pop your ult as well.

With Zhonyas it is unbelievably simple:
you get in there, make sure you have popped your ult.
You pop Zhonyas before you die, then your team will follow up and kill them.
you celebrate the victory with a baron and a nexus exploding.

What I like to do, is to use Q for last hitting the creeps, if mana gets to be a problem, get used to the AA. In terms of trading, make the fight while a short time, cause after your combos, you got nothing.

Rod of Ages
+60 ability
+300 health
+300 mana
This item is a constant first item for Swain. Its unique passive works really well with Swain's abilities, and makes him a very tanky mage to play against.

Sorcerer's Shoes
+18 magic penetration
+45 flat movement speed
If you are doing well early game I would advise buying this item because it gives you magic penetration which makes Swain's abilities more powerful.

Liandry's Torment
+80 ability power
+300 health
Liandry's goes well with Swain's passive and gives you some tank shred so you can kill more hefty opponents.

Ludens Echo
90 Ability Power
10% Cooldown Reduction
600 Mana
Well, this May just be me, but this items i crazy in my opinion, make waveclear way easier with Q + E.

Passive: Ravenous Flock

Ravenous Flock
Ravenous: Swain can right-click an immobilized enemy champion to pull them towards him, ripping out a Soul Fragment and dealing (20-105 based on level (+30% AP) magic damage (12-6 second cooldown based on level)

Flock: Enemy champion deaths create a Soul Fragments. Swain can collect Soul Fragments to restore (4%-7% total health)

Swain can store up to 5 Soul Fragments.


Q: Death's Hand

Death's Hand
Cost: 65/70/75/80/85 Mana
Cooldown: 7.5/6.25/5/3.75/2.5

Swain unleashes FIVE bolts of eldritch power that strike the first enemy they hit and pierce through enemies they kill. Enemies hit take 65/85/105/125/145 (+40% AP) magic damage, plus 15/20/25/30/35% per additional bolt. Max Damage: 104/153/210/275/348 (64/72/80/88/96%AP)

Each unit killed by Death's Hand restores 3% of Swain's Maximum Mana.


W: Vision of Empire

Vision of Empire
Cost: 90/100/110/120/130 Mana
Cooldown: 22/21/20/19/18

Swain opens a demon eye up to 3500 range away that deals 100/150/200/250/300 (+70% AP) magic damage and slows for 25/35/45/55/65% for 2.5 seconds.

Champions hit grant Swain a Soul Fragment and are revealed for 4/5/6/7/8 seconds.

Damage is reduced by 50% against minions.


E: Nevermove

Nevermove
Cost: 60/65/70/75/80 Mana
Cooldown: 13/12/11/10/9

Swain launches a wave of demonic power, dealing 35/70/105/140/175 (+25% AP) magic damage to enemies it passes through.

Swain then commands the wave to return, detonating it on the first enemy hit. Enemies hit take 35/45/55/65/75 (+25% AP) magic damage and are rooted for 1.5 seconds.

The target will take a total of 70/115/160/205/250 (+50% AP) magic damage if they are hit both parts of the wave.


R: Demonic Ascension

Demonic Ascension
Cost: All Soul Fragments
Cooldown: 120

Swain frees the demon within for 12 seconds, gaining 150/275/400 bonus health. Every second, he drains the 3 closest enemy champions for 35/50/65 (+14% AP) magic damage, healing him for 15/30/45 (+16% AP) health. After draining 150/300/450 health (based on level), Swain gains the ability to cast Demonflare.

Demonflare: Swain unleashes a nova of soulfire dealing magic damage and ending his transformation. Damage per Soul Fragments: 45/60/75 (+27% AP) for a maximum 225/300/375 (+135% AP) damage with 5 Fragments.

Swain can drain non-champions to heal for 20% of the normal amount.