I played the preset kingdom from dark ages mixed with hinterlands that was the following board.
Altar, Catacombs, Ironmonger, Poor House, Storeroom, Crossroads, Farmland, Highway, Spice Merchant, Tunnel.
I will preface the combo with how the game looked like for me.
I had the 5/2 opening but Im confident this strategy would have been dominant with a 4/3 as well. We started with shelters instead of estates.
Buy Highway, Crossroads.
Buy Estate trashing hovel, Buy Highway, Buy Spice Merchant.
Since Crossroads gives 3 actions I bought 3 altars the first one off of a highway buy and later ones off of play highway play alter trash a card gain altar.
Now Spice Merchant is eating my copper, so my highways are consistently hitting and altars are gaining me additional highways. Later on I play at least 3 highways a turn and play altar to trash 3 cards from my hand into provinces. Because Provinces now cost 5 and unlike other TFB cards none of them have a set value until now.
So the idea of the combo is to use Altar to get highways and highways to get altars, play at least 3 highways and you can altar cards into provinces. You will obviously want some form of +actions and some form of draw once you start greening (luckily crossroads did both for me). But if I had a village catacombs would have worked as well.
In a colony game I think this is still viable but will be more dependant on having actions and draw because you'll need to play 6 highways in order for altar to do its thing which also means you'll need to win the highway split.
This is very much a work in progress article but I wanted to get the rough idea down while coming fresh off of playing this game (all input is welcome)