If you don't have Tess - The Magician yet but want to try her out, she is available as a Trial Operative in most missions of Story Chapters 12A and 12B (Legacy //Yehrus)
Tess is a U-Energy battery, with her ultimate giving a huge amount of U-Energy, allowing other operatives to use their ults immediately.
Tess is basically useless for everything else other than providing a single huge burst of U-Energy.
Role: Support - U-Energy battery
Electric Damage
Weapon Type: Sniper Rifle
Deals basically no damage
(but entirely ballistic)
Mobility is good
Just spam her support skill and ultimate off-cooldown.
Weapon: Eccentric Joker / Wasp or Deep Sea's Call
Weapon Parts: Max ATK
Logistics Squad: Hjartagard
+14.1% U-Energy Recovery
+106 Alignment Index
+8.5% Electric Damage
Good dps operatives for Tess to support
Enya - Tempest
Fenny - Pureheart
Fritia - Hush
Ultimate Skill
For 25s, whenever any operative shoots an enemy, Tess deals electrical damage and recovers 5 U-Energy.
Tess can attack every 2s.
The 2s cooldown means that the dps is not that high, and you really only want to use Tess' ult for the U-Energy.
When this ends, you lose all U-Energy.
As such, you ideally want to either use all your U-Energy before it ends, or make sure you don't need your U-Energy after that.
This has a 150s cooldown, and the cooldown starts after the 25s duration ends.
This very long cooldown means that you can probably only Tess' ult once per fight.
The skills second Neuronic buff does reduce its cooldown a bit, but it's still very long.
Support Skill
Tess gives a 30% damage DMG buff for 10s. This decreases by 1% per second.
This is by-default an Electrical dmg buff, but with its first Neuronic buff the damage type changes to match the current operative.
WIth its second Neuronic buff, Tess gives an extra effect based upon the daamge type of the deployed operative; (Stunned, Burn, Frozen, Paralyzed, Slow, respectively)
The Burn lasts 10s, but the other effects last 2s.
Standard Skill
Tess throws a card at enemies:
White Card - Deals Kinetic damage, replenishes 2 bullets, an deals extra destructible object damage.
Red Card - Deals AoE Thermal damage and burns the targets for 12s.
Blue Card - Deals Frost Damage, and applies Frozen for 2s.
Yellow Card - Deals Electrical damage, and reduces the skills cooldown by 3s.
Pink Card - Deals Chaos damage. If it doesn't kill the enemy, then deals Chaos AoE damage.
The colour Tess uses is random each time.
This skill has a 6s cooldown and uses only 5 S-Energy, and Tess shooting an enemy reduces the cooldown by 0.5s.
This makes it quite spammable, but the damage isn't that high, and the moderate cooldown means its dps isn't that high.
Eccentric Joker
Tess' 5*, and her best weapon.
Gives more max U-Energy, and increases U-Energy regen and all-damage types. This buff is doubled when Tess isn't on-field.
Wasp
For 20s after using her ult, gives +1.2-2 U-Energy each time they deal damage.
With a 2s cooldown, this gives a maximum of +24 to +40 U-Energy, which is good, but with Tess' ultimate this probably isn't necessary.
Deep Sea's Call
The usual sniper for support operatives - giving a +ATK boost for 15s after using Tess' support skill.
Both Wasp and Deep Sea's Call are good, but do very different things.
Use Hjartagard squad - it was designed specifically for her and is her best choice.
For stats Tess wants +106 Alignment Index and +U-Energy Regen.
For the Special talent, Tess wants 8.5% Electrical Damage
Tess does deal damage, so +Electric dmg does help her, but Tess' dps isn't good, so +Electrical dmg is her best special talent, but isn't very impactful.
U-Energy regen is a great stat for Tess, as U-Energy regen is the only reason to use Tess.
Alignment Index gives
+20% U-Energy Regen if below 50% U-Energy.
+20% S-Energy Regen if above 50% U-Energy.
Three +106 Alignment Index mods give +15.9% regen, which is good.
Again, the only reason you're using Tess is for the extra U-Energy, so the regen from Alignment Index is great for Tess.
M1 gives Tess' ult an extra 1 U-Energy per proc, increasing by 1 U-Energy each time.
This totals an extra +55 U-Energy, and is a large amount of extra U-Energy.
M2 gives an extra +20 U-Energy after using Tess' ult.
Again, a nice amount of extra U-Energy, which is the main reason you are using Tess.
M3 allows any attack to proc Tess' ult, not just shots.
M4 gives Tess' ult +1 level, increasing its damage.
M5 gives Tess' ult the same damage buff as her support skill.
This is a nice buff, and allows much higher uptime on her support skill.
If you want efficiency (good damage without massive investment), then M2 is a good stopping point.
M3 is useful for skill-damage operatives, but isn't useful for ballistic operatives.
The only reason you'd use Tess is for her to provide large amounts of U-Energy.
Tess' damage bonuses are low, and she doesn't debuff enemies, so if you don't want U-Energy then Tess is basically useless.
Tess' effect on your sustained dps is very low, and hence you only want to use Tess to provide U-Energy for operatives that can end a fight quickly using that U-Energy.
Tess is a useful support for operatives that can use their ults quickly to deal very high damage, ideally one-shotting bosses, or at least using it to deal huge damage.
Enya - Tempest
Tempest can use her ult to deal extreme damage almost immediately.
Fenny - Pureheart
Pureheart's ult deals extra damage based on how much U-Energy Fenny has, so Tess can add a lot of damage to Pureheart's first ult.
Fritia - Hush
Hush' ult is where almost all of her damage comes from, and Hush can use all U-Energy to sustain her ult.
Tess allows Hush to use her ult and start dealing damage extreme immediately.