Death Foursworn

Not a hard achievement, if you get the strategy down.

Use Pelagos. Equip the Trident.

Take out the phylacteries in this order: Pain, Suffering, Death, Destruction

Position yourself between Pain and Suffering before beginning. You can destroy a phylactery with one Test of Faith and one Aspirant's Bindings. There's no need to use two Tests of Faith on one phylactery, so don't! Use your Confront Memories invulnerability one time while you're taking out the phylacteries in order to save yourself some damage.

When all phylacteries are down and you're able to finally dps Thran'tiok, try to avoid Death Blossom, but save your Confront Memories invulnerability for the occasional time that you have poor positioning and will be hit by it.

Watch for Terminal Destruction and use the trident to stop the cast.

This is a very easy fight

Boss abilities
Necrotic bolt. This is a small damage attack that can be ignored.
Terminal Destruction. He will cast this as long as he has phylacteries up. It can be stopped with deep echo trident and takes a while to cast. He will get a cooldown after casting it to prevent him from spamming it.
Greater Necrotic Bolt. Same as the Necrotic bolt.
Death blossom. He will cast this after all the phylacteries are broke. It is a circle that grows the further away it gets from him. You want to step into the safe zones to avoid damage
word of suffering which places a debuff on you, this can easily be absorbed by confront memories shield. He also continues to cast terminal destruction now even when her phylacteries are destroyed

On wisdom she can continue to cast all the spells when the phylacteries are broken

Boss strategy
For this choose Pelagos and for equipment choose the vial of serenity for heals. If you interrupt her it will not count the achievement. Simply Destroy the first phylactery which will make the boss lose his shield for 20 seconds and take 20% more damage. Make sure to stand behind the pillars as this will prevent boss from casting necrotic bolts because of the LOS. It will not stop the other spells. Rinse and repeat till all 4 phylacteries are broken Take your shield from confront memories to avoid damage with terminal destruction. Now you will want to make sure to time your confront memories shield at this point as death blossom will ot trigger it. This way you can absorb both word of suffering and terminal destruction. Dps down boss and profit.

Wisdom With Pelagos and death foresworn achievement
New ability is she can cast all the spells from the broken phylacteries. To mitigate dmg you can line of sight her necrotic bolts.
https://www.youtube.com/watch?v=oGFavTzpJiQ

Very easy in 10.1.5
• Select Thran'tiok
• Select Trial of Wisdom
• Select Pelegos
• Ignore Charms & ‘equip’ items
• Enter the fight
• Stand right back and target each phylacteries in any order (I used Test of Faith)
• Once done burn the boss
Achievement pops
Grats