Welcome to the Tank Lissandra Support guide! I am a very new Lissandra player, but I have seen this been played by a few youtubers so I thought I would give it a try and it works out great and it is extremely fun.

For the items I chose a couple of new items and combined it with some AP items as well to get the best Lissandra support build. Your core items include the new Evenshroud and Winter's Approach items as well as boots and the reworked Demonic Embrace. Evenshroud it a great item because like Leona you will be up in thier face, CCing them allowing your team to do more damage to the enemy. Along with that you have Winter's Approach/Fimbulwinter, a new tank mana item built from Tear of the Goddess and was actually ported over from Wild Rift. The items is great because it gives lots mana, HP, and a shield when you slow or immobilize(hit an enemy with hard CC). After building boots you will build a great newly reworked item in s12, first itroduced in s11, Demonic Embrace. Demonic Embrace is a much better item now because it give you AP based on total hp and works amazing with this build because all 3 items give a ton of HP as well as most of the final items you will build. For the final items all you need to build are items that are good against the enemy comp you are against to become even more tankier.

For you runes you will be going a standard engage support rune page. You will be running Aftershock which is easy to proc and use with your main combo of E into W. Next if Font of Life which is just generally a good rune to have on engage supports because it activates off slows and hard cc and allows your ADC to heal off of whoever has been marked with it. Next is boneplatting which gives a highly needed sustain in lane and gives her some beefyness so she doesn't get bursted down when engaging. For the last rune in the resolve tree run either unflitching if there is a lot of Hard CC or Overgrowth to become insanely more tankier and allows your demonic embrace to scale up even better, giving you more AP. For secondary take biscuit delivery to make sure you have enough sustain in lane before you get and can stack up your tear, and cosmic insight just to be able to have your Hourglass and summoner spells up quicker.