The Lux build for Support is Luden's Tempest and Dark Harvest. This LoL Lux guide for Support at Platinum+ on 13.19 includes runes, items, skill order, and counters.
Lux Counters
Luxwinslane against...
Win Rate
Matchup Rate
Milio
1274 games
1.4%
Janna
1371 games
1.5%
Rakan
3419 games
3.7%
Alistar
2113 games
2.3%
Braum
993 games
1.1%
Renata Glasc
1087 games
1.2%
Soraka
3061 games
3.3%
Sona
1217 games
1.3%
Nami
3132 games
3.4%
Shaco
896 games
1.0%
Leona
2460 games
2.7%
Rell
1223 games
Lulu
3195 games
3.5%
Thresh
7233 games
7.9%
Maokai
564 games
0.6%
Nautilus
4816 games
5.3%
Taric
618 games
0.7%
Morgana
3407 games
Blitzcrank
4216 games
4.6%
Seraphine
1663 games
1.8%
Ashe
563 games
Bard
1672 games
Yuumi
2218 games
2.4%
Swain
1898 games
2.1%
Karma
3489 games
3.8%
Brand
2275 games
2.5%
Zyra
3757 games
4.1%
Zilean
1128 games
Heimerdinger
544 games
Luxloseslane against...
Bel'Veth
934 games
Xerath
5126 games
5.6%
Vel'Koz
1174 games
Twitch
537 games
Neeko
1130 games
Pantheon
1088 games
Senna
5337 games
5.8%
Pyke
3372 games