Before we get into the new expansion, I wanted to take the time to look back and see which new region combinations that Targon created with viable decks/archetypes and what worked and didn't work. While at the start it seemed like Targon won't really be compatible with many regions due to the focus on only 3 other regions (SI, Ionia and Freljord), there have been more decks that have popped up than anticipated.
Targon + Ionia = This was pushed heavily in the first expansion but it didn't really pan out the way that Riot intended. It was very clear that the theme of Ionia + Targon was going to be spell + buff oriented with support synergies between Lulu and Taric. What ended up happening is that the archetype morphed into a combo deck revolving mainly around Lee Sin and using many gems to proc the level up as well as Zenith Blade and Bastion to enable Lee Sin to single handedly win the game. Yes Zed is in this deck too sometimes but this is almost entirely a Lee Sin combo deck. Curious to see if the Targon + Ionia support package gets more support in the future or if Taric receives buffs. Lulu at least is relevant in Ionia + Demacia decks.
Targon + SI = This was pushed hard with the Nightfall archetype and I have to say it met expectations and exceeded them in some regards. Definitely a solid tier 2ish deck that plays for tempo with a sort of unique take on quicker decks as far as LoR is concerned. This is probably the most rigid archetype and really needs a lot more Nightfall cards and synergy cards to allow for it to be played in any other way aside from "CTRL+F" deck build. Diana and Nocturne are actually solid champions but Nocturne only works in this type of deck. Without future support, this deck might just get power crept out of the game completely.
Targon + Freljord = Initially the most successful new archetype presented in the expansion which is the Ramp ASol deck being carried hard by Trundle. Trundle is a super versatile mid to late game champ combined with Asol + Mindsplitter has resulted in a meta game that is slowed down considerably and late game plays are much more viable. The existence of this decktype also resurrected the Warmothers archetype as a way to play into the late game. Asol was nerfed just recently but this deck is still strong and played quite a bit though is being out performed by Warmothers usually.
Targon + Demacia = New archetype that is similar to Targon + Freljord but splashes Demacia for some mid game control in the form of Lux and Radiant Guardian (which was just recently nerfed). I feel like depending on if they support Demacia in this upcoming expansion, we'll see a lot more Dragon D+T type decks in the future. Currently being propped up heavily by Mindsplitter + Asol. This is also the type of deck that utilizes a Targon allegience deck.
Targon + P&Z = This was played with Ezrael initialy but was abandoned when Ezrael was nerfed and then replaced with Heimer Targon when Flash of Brilliance was buffed. A lot of people have spoken well about this new Heimerdinger deck though the deck isn't as popular as one might expect. The numbers are improving overall and once this decktype is refined it will make an impact. Also worth noting that Bastion buff was huge for this deck as well.
Targon + Bilgewater = So far I have really only seen Swim prop up this region which basically plays similar to Ezrael TF only removing Ezrael since he is much worse now and going more all in on draws and protection on TF. I have played this deck a few times personally and I really don't think it's that great mostly because without the key P&Z cards like Mystic Shot and especially Thermo Beam, the deck lacks way to interact with the opponent's board before TF is flipped/Rex is played. That said these new Tahm Kench Bilgewater card might work well with Targon due to gems, heals and buffs. We will have to wait on that, maybe Soraka is the key.
Targon + Noxus = Before the expansion was released, people were theorycrafting Draven + Taric decks with focus on buffs and overwhelm. That didn't end up panning out past the initial week and I don't think Riot will be supporting this archetype much at all anyway. Curious to see what their plan for Noxus is as that's the most unknown archetype aside from a new P&Z archetype. Please more stun synergy for my boy Yasuo!