Best secret tech mods?

[plugwater]

What do you guys think? For me, I think Mark of the Dark Sun is quite good.

[Ddraig Lleuad]

Depends entirely on how you define 'best', I think.

[Roderick]

I love the prometheans from start to finish. Purification field and hazmat protection are great at the start. Together with a stubborn leader you may run into any encounter. As long as the enemy isn't overpowering you greatly, you can withstand or negate almost everything they throw at you.
Later on, since I like touse infantry, the Phoenix Bomb Launcher provides nice attack and defence. ^^
Just don't use hazmat protection on the Phoenix Walkers. xD

(Probably not so good in pvp, but I stilllike it the most.)

[Janthis]

It depends on what faction you're playing, but Celestians, Synthesis and Promethean all have some great early game mods and ops.

Celestians get Cleansing Light, which heals a unit and removes all negative effects, and Tenets of Tranquility, which makes them Enlightened, gives a level of stagger resistance, and increases morale.

Synthesis get the Offensive and Defensive Integration mods, which are great to have on any unit in the early game.

Prometheans get the Purification Field which once again heals and removes negative status effects, and most importantly, it's a free action.

There are other notable ones too, like the Heritors mod which gives energy drain on melee attacks plus an AoE ability. Gotta experiment and learn them all. :)

[Reality]

TLDR Best for me - All 100 Research Mods + Xenografted Muscles + Thermal Targeting Relay + Shield of Remorse. I like the best hits from cheap research more than the big boys.

My favorite expensive secret techs are Bio Spore Hyper Aggresion, Avatar of the Abyss, and Phoenix Bomb Lauchers... I think that the Defensive/Tanking Oriented Ultimate Mods (Synthesis/Celestian/Voidtech) are objectively the absolute strongest (Talking about FFA or 1 Human 7 AI super lategame), but they're BORING to play with. If I'm going to commit to spending multiple days on a single game I need my ♥♥♥♥♥ and giggles.

Per Research Cost

100 (All 7 Secret Techs)
Super Competetive, since almost every faction has things you can splash on nearly every unit for the earlygame and midgame, and still see occasinonal use in lategame.

Also important that you are slapping this on things from turn 3 of the game and a lot of them let you go nuts clearing neutral camps and Landmarks.

Promethean > Celestian > Synthesis > Psynumbra > Heritor > Xenoplague > Voidtech

Turn 3 Mass Self healing / stagger resist / Evasion are all pretty crazy and still valuable lategame. The offensive oriented mods aren't bad either, but they don't contribute to rushing landmarks with starting army + 2-3~ manually built infantry as much.

150 (Only Celestian)
Celestian wins by default since it's the ONLY 150 Research ST Mod (ALL others get their second mod at 300 or later).. That said Remorse is super annoying when fighiting an army full of high HP units (Which Celestian is great at since most of its mods add HP)

300 ( Everyone EXCEPT Celestian + Psynumbra)
Promethean > Xenoplague > Heritor > Synthesis > Voidtech

Promethean's Thermal Targeting is special because of effiency - the majoriy of +30% damage Mods take 15 cosmite, while this takes only 5 (Technically it is conditional, but having spare Purifiers/Phoenix Walker isn't that hard of a conditon to meet). Xenoplague Upgrading High Impact Stagger to Massive Impact Stagger is also pretty notable, since it makes their Pustules/Destroyers much more dangerous... however most of the good Tier 3 Racial Melee units have massive stagger already (Kirko,Assembly Wrecker, Oathbound Champion) and Destroyers start evolving into Plague Lords, so it's kind of early/midgame oriented.

520 (Everyone EXCEPT Voidtech + Xenoplague)
Heritor > Celestian > Psynumbra > Synthesis > Promethean

I kind of think of it as a weak research tier... Free Action Essence and a 7 range heal are nice, but paying 10 cosmite per instead of 5 and/or built into the unit kinda hurt. Psynumbra gets honroable mention pretty much for being a midgame survivability option for Malictors, who can use it for the stretch of turns before you can research their proper endgame army stuff.

800 (ONLY Voidtech + Xenoplague)
Xenoplague > Voidtech

A heal you can slap on anyone is nice... but this amount of resarch is a long wait. The Grenade is bad like most grenades, I guess the idea is that Echo Walkers slightly redeem it by getting to use it twice, but this applies to any single use abilitiy (Echo Walkers ironically make crazy good use out of almost every NON voidtech once per battle mod)

1200 (Synthesis, Celestian, and Heritor ONLY)
Synthesis > Heritor > Celestian

A Deployable Summon that you can use on multiple units is lots of fun even if it's not as beefy as the common hero item drones. Celestian gets a powerful status effect with not a very impressive chance of landing, other lategame status effects tend to have an almost as good "if resisted" effect but this is all or nothing on top of being an awkward full action abiilty.

1700 (Everyone EXCEPT Synthesis and Celestian)
Heritor >Xenoplague > Psynumbra > Voidtech > Promethean

Heritor gets the EZ way to get Essence charges on its whole army (essentially an extra +1-2 hero shield auras on top being able to use all its essence charge spending attacks easier). Xenoplague gets a damage mod that can benefits multiple units. Psynumbra is no joke because while 4 is a low inflict chance... with malictors it's hitting 3 guys 3 times (9 attempts) and you are boosting the inflict chance another 2 levels with each broken mind.... that said it's obsoleted if you don't even need the "disable". For Voidtech Certain (mostly racial) heavy units gets extreme benefit from a Teleport, but other factions have all repeating actions on their T3 units at which point you are mostly taking it for the +2 Shield which can be done with lower cosmite mods.

2750 (All 7 Secret Techs)
Synthesis > Celestian > Voidtech > Psynumbra > Promethean > Xenoplague > Heritor

Pretty much all of these make an army that can only be fought by an army with another of these techs (there's a reason why this costs so much more cumulative research than unlocking tier 3/tier 4 units themselves) so "best to worst" is kind of redundant.
I think Promethean is number 1 on "fun factor"... turning Tier 1 Infantry into the highest damage artillery in the game is hilarious.