I've done a lot of experimenting in LOL and honestly most of my builds are extremely situational and work maybe a couple of times a game and either I get giga fed or just int. HOWEVER, this is not one of those builds. Bruiser/Tank Lillia is straight up busted. I almost consistently get top 2 damage on my team and almost always take the most damage. All this with a clean KDA.

You should play this because tank/bruiser Lillia is:
- Tanky
- Speedy
- Deals Damage
- Fun to Play

The whole build revolves around your passive's ability to heal you and the fact that Lillia is actually a really good team fighter and 1v2 duellist if you don't get immediately killed. So if you hit over 3k health with some good resistances, you do all kinds of damage whilst still healing.

Lillia's passive, Q, W and R all have good base ability without needed to build to much AP. At level 1, your W will do a third of most mid-laners health bar, your R is a utility ability and so you don't even need damage. Your Q however does need some sort of AP added to actually hit hard, but with the true damage and AOE application of burn from your passive it only needs about 200 AP added to be enough for the whole game.

So pretty much the whole idea is that you get riftmaker and spirit visage for the healing. This essentially allows you to run around and heal with your passive and q damage.

After that I normally go mostly tank with some health-AP items. You can mix and match but brambles/oblivion orb is a must most of the time.

Boots are up to you. If you have tenacity runes I would just get tabi, otherwise its pretty situational.

Take electrocute as jungle, comet for support, conqueror for top and then decide between comet and conqueror for mid/top. The rune choices are mostly just based around the extreme need for mana and getting runes that increase your healing.

I mostly play this mid, so most of this will be from that perspective but it works the exact same for top, support and jungle. The main thing you need to be careful of in lane is your mana. Most of the time I die is because I don't have enough mana to use my abilities. That's why I have mana runes (POM or MFB) and sometimes start tear or get frozen heart (normally for support).

EARLY:
You often win early into melee matchups because you can hit them with the edge of your Q and then back up so they can't engage. On melee champs you can also hit your W more reliably early on (which does 250+ damage level 1). On champs with good poke (ranged), you probably just want to wait until you get riftmaker and then teach them to be careful who they bully in middle school.

MID:
Once you get riftmaker or if you get a couple of kills early so that your laner respects you enough to just farm, I would try to roam and help out your jungler with ganks. Just with riftmaker you can normally 1v2 enemy champs especially if they don't respect your damage (watch out for hard CC though).

LATE:
With a couple of items you want to be team fighting. Plenty of times I have been able to get away from 4 people chasing me but only been able to kill maybe one because the damage output isn't there. This build is supposed to be more drain tank where you stay alive for a long time and chip away at their health whilst you just heal through their damage. So if you have a good support that can stun them and occasionally heal/shield you, you can normally 2v4 or 2v5. Otherwise team up with the biggest damage dealer on your team and then just duo lurk with them and kill anyone you see. Works surprisingly well.