Swain

Strengths

If you're having trouble rooting an enemy with Nevermove, try throwing it at opponents when they are near their minions so the explosion surprises them.
While laning, try to use Death's Hand's piercing damage to damage opponents from a safe distance.
Vision of Empire is quite difficult to land on its own, look for skirmishes around the map where enemies may be distracted or crowd controlled so you can land it more easily.

Passive · Ravenous Flock — Swain's ravens collect Soul Fragments that heal him and permanently increase his maximum health.
Q · Death's Hand — Swain unleashes several bolts of eldritch power that pierce through enemies. Enemies hit take more damage for each bolt they are struck by.
W · Vision of Empire — Swain opens a demon eye that deals damage and slows enemies. Champions hit are revealed and also grant Swain a Soul Fragment.
E · Nevermove — Swain launches a wave of demonic power forward. It then returns to Swain and roots enemies it hits. Swain can then choose to pull all rooted champions closer. This ability has a shorter cooldown during Demonic Ascension.
Ultimate · Demonic Ascension — Swain transforms into a demon and drains health from nearby enemy champions, minions, and neutral monsters. Swain can cast Demonflare to decimate and slow nearby enemies with a nova of soulfire. This form is indefinite as long as Swain drains enemy champions.

A suggested 5-lane lineup built around Swain, based on hero partnerships and role synergy — not win rate.