The Cuotl have perhaps one of the most interesting methods of healing in the game. It's pretty hard to figure out, so I'll break it down for you:
The Alin and Vinci each have a tech line (Vigor for Alin and Prosperity for Vinci) that, when researched, turns on and then increases the healing done while standing stationary in friendly territory. For each level you get 1, 2, 4, and 7 hp/sec healing respectively.
But the Cuotl are different. The Cuotl don't have a tech line for healing, instead they build Holy Districts at their cities to grant healing to stationary units in their territory. Each holy district adds .25 hp/sec healing. A palace district will double the effectiveness of Holy Districts in that city. So if you have 2 Holy Districts in your one city, your units heal at .5 hp/second. If you add a palace district to that city they heal at 1 hp/sec (everywhere in your territory, not just around your city).
The Cuotl also have a secondary method of healing, their Holy Ark. You can build the, what I like to call "Stupid Expensive" Holy Arks at a city, but the most easy way to get them is to build a Holy District, then you get one for free. Holy Arks are good for speeding up production of your barracks-type buildings, as well as increasing border push of Sanctuary and attack of Obelisk.
Worship is what's important when it comes to Holy Ark healing. Every level of Worship increases the Holy Ark's healing by .33 hp/sec. The ark starts at 0, so researching Worship lvl 1 will enable the Holy Ark to heal everything friendly inside it's radius at .33 hp/sec. Lvl 2 makes this .66, level 3 makes it 1 hp/sec, and Level 4 is 1.33 hp/sec.
What's great about this though, is that you can have your units healing always. Units in Vinci and Alin armies have to stand still in friendly territory to heal, but Cuotl units can be always healing, even when moving/fighting!
What's even better is that this bonus stacks with the "territory heal" bonus described above. So if you have 5 holy districts and 3 of them are in large cities (2 hp/sec just for territory heal) and have your units standing next to a holy ark with level 2 worship (.66 hp/sec) you'll get a grand total of 2.66 hp/sec healing!
"Wow," some of you are saying, "that's actually not that great compared to Vinci/Alin 4 hp/sec heal rate at lvl 3 Vigor/Prosperity. This is true. The Vinci and Alin can get their units back to max health relatively quickly by letting them stand in their territory. But remember that Cuotl can heal while on the move, so effectively they are healing every second of the game after you research Worship 1 (as long as you keep Holy Arks with your army) .
This is important, because Cuotl rely on a small number of more powerful units to defeat their enemies, so keeping your units alive is critical to playing Cuotl correctly. Whereas playing alin you can make suicide runs on a mine just to kill off the miners and it cost you maybe 70T for the 2 squads of DW, you can't afford to sacrifice Sentinels this way. Using the Cloak to get very-hurt units back out of the front lines is a great tactic, but don't blanket-cloak your army, that costs a lot of energy!
Hope this helps the aspiering Cuotl players, or perhaps helps the Alin/Vinci players understand the importance of targeting those Holy Arks
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