#1 - Character Zeniths. Go to the character page. Most characters do not have it unlocked yet. Themed versions of characters can pool ZP together. Max of 15 stars per character.

List of current zenith characters
Gawain
Altair
Gandalf
Birdman
De La Fille
Lady Grey
Yuel
Lily
Light Sarunan
Cagliostro
Charlotta
Magisa
Wind Metera
Seruel
Io
Cerberus
Male Megumin
Razia
S. Beato
Casual Zeta
Orchid

Notable SRs
Helnar
Gayne
W. Sutera
Soriz
Mina
Albert (SR)
Tire
Lyria
All story SRs

#2 - Seraphim Battles. Go to the Shop, then Weapon Series. You have to buy the initial SR for that element to get the fights (which are under special). You can only do 2 seraphim fights a day across all elements and difficulties. The SRs also require new treasures from the rotating elemental quests. Weapons multiply damage at the end of the damage calculation (avoids damage cap) when on-element. 10% at SR, 20% at SSR.

#3 - Rose Queen Weapons/Distinctions. Under Treasure Trade -> Treasure, you can trade for up to 10 distinctions (a month?) or trade for a rose, which is used in Rose Queen Weapons (new unknowns with on-element resist). Find those under the Quest Items tab.

#4 - Misc. You can use weapon skins for anything you have ever picked up (as long as it is the same type as the weapon you're wielding).

#5 - GW Character 5*. Coming March 20th along with T4 Superstar.

Uno:
-reduce cooldown on 1st skill
-2nd skill also gives massive self atk up
-4th skill cuts all elemental damage by 50% and absorbs damage for 3 turns (can't be used again but have to wait for 10 turns to use it)
-ougi gives party frontwater effect and barrier
-1st passive has chance to cut damage by 50%
-2nd passive gives damage up against fire

Song:
-1st skill now gives ability cap up
-3rd skill is AoE but deals more damage against fewer targets
-new skill extends debuff duration and deals AoE damage based on no. of debuffs (up to 10 hits)
-ougi gives party crit up
-1st passive increases self atk against fewer enemies
-second passive increases debuff success rate against fewer enemies

Sarasa:
-2nd skill gives self atk up in axe mode and hostility down in sword mode, cooldown reduced
-GZ now does earth resist down and cooldown reduced
-new skills is 4 turn ougi 100% recharge + one turn atk massive up
-ougi gives self earth atk up in axe mode and two-hit 999999 damage in sword mode
-1st passive gives crit up when angered, echo when enraged
-new passive gives damage up against water(edited)

Quatre:
-1st skill gives 2 random debuffs
-2nd skill hits 6 times and now dispels
-new skill lets him use his damage abilities up 4 times + debuff success rate up
-ougi gives party DATA
-1st passive gives debuff success rate up
-new passive gives damage up against fire

Funf
-1st skill gives party heal + revitalize and cooldown reduced
-2nd skill gives party debuff resist up and cooldown reduced
-new skill gives party revive + full heal + guts (i.e. resist death once)
-ougi gives enemy dark atk down and DATA down
-1st passive makes him immune to skill seal
-2nd passive reduces party's dark damage received

Six
-1st skill now gives stackable damage cap up/ hostility down
-2nd skill now counters 3 times and last 2 turns
-3rd skill now makes him invincible once
-4th skill dodges all attacks for 6 turns
-ougi gives dodge rate up
-new passive is chance to counter when damaged(edited)

Siete:
-1st skill now gives 2 Lvs of sword shine, which stacks up to 5 Lvs, duration increased to 5 turns
-2nd skill gives 30% ougi charge and has cooldown reduced
-new skill gives party ougi damage up + ougi cap up + party ougi 100% recharge when swordshine is Lv3 and above
-ougi now gives once invincibility
-1st passive now breaks party ougi damage cap
-2nd passive increases damage against earth

Okto:
-1st skill gives self ougi damage and ougi cap up
-3rd skill gives stat up based on absorbed ougi gauge
-new skills gives self uplift (70%) for 5 turns
-ougi gives massive self DATA up and party earth atk up for 2 turns
-1st passive increases DA rate
-2nd passive increases damage against water

Nio:
-2nd skill gives special atk up and DATA up (same type as Korwa's buffs, won't stack)
-3rd skill gives 2000 barrier
-new skill gives party guranteed TA and 50% wind echo for 4 turns
-ougi now extends her special buff
-1st passive reduces damage received from tuned enemies by 20%
-new passive increases damage against earth

Esser:
-2nd skill now breaklocks
-3rd skill now gives self buff based on TH
-new skill gives party buff based on TH + BA
-ougi increases party skill damage
-1st passive increases drop rate by 10% + chance to deal massive crit damage
-new passive increases damage against wind

Their new passives don't stack with seraphim weapons