The whole point of this build how to make yourself unkillable. By this time you hit your three item spike, it will be virtually impossible for you to be killed in a team fight if you position properly. The combination of your new passive with stacking HP, high levels of armor and magic resist from your items, the tankiness of your runes, and the build-up strength you get in a team fight from Liandry's Torment; all of these will lead to an unstoppable mid game.

Play Swain top for more gold income and a chance to scale;
Play Swain bot for more Soul Fragments, two-v-two potential, and kill threat;
Play Swain mid for more map pressure, gold income, and early game impact.