So, you haven't played nightreign in a few months and came back for the dlc. You want to play the deep of night mode so you queue up on erg, you're immediately thrown in a Depth 5 game where you hopelessly die constantly and fail your team. What can you do to prevent this from happening next time? Let's begin with relics.
RELICS
You need to equip a relic with "Attack power increased for each night invader killed". This will be the most important relic effect you can have, it doesn't matter if the other effects on the relic are useless, as long as you have one with night invaders you're good. Night invaders are the new meta for getting strong fast, they are the new gaols basically so make sure you have one equipped for all your builds. Because the Great Hollow can now appear in depths, it's better to drop gaol relics as a whole and use something else. For melee I recommend both balancer relics so you can spam whatever AOW you find and still do good damage. As for deep relics, there are some effects which are mandatory per class. These include: [Wylder] Skill inflicts blood loss, [Ironeye] Inflict heavy poison damage on poisoned enemies, [Duchess] Invulnerability on Skill use. If you're playing a caster, it's better to forego damage negation effects and fully focus on DPS with your relics.
Some deep relics come with debuffs. Here's a list of debuffs you absolutely have to avoid: continuous hp loss, all resistances down, poison/rot build up below max hp, near death reduces max hp, and anything with increases damage taken after evasions/dodging. There are also relics that can have "dormant power helps discover X", these will replace the preferred weapon of your class within the loot pool. They do not have an effect if the weapon belongs to the class, such as dormant power greatswords on wylder or sacred seals on revenant.
CLASSES
At Depth 5, raider and guardian have become obsolete. Do not play them. You will only be a detriment to your team and you can probably figure out why. Thank you.
PASSIVES
The single most important passive now is damage negation at full hp. You should try to stack two of these in every run. Always check the merchant if hes selling one. You can stack them if they're the same tier (IE, two blues or two purples) but this does not apply to the following passives: successive attacks negate damage, taking damage boosts damage negation, damage negation up with charge attacks, casting spells ups damage negation. This means you can't stack two blue successive attacks negate damage, the 2nd one must either be white or purple tier. Also, make sure to check your teammates relics and inventory so you can drop any loot they might want. If you see they dont have any defensive passives by day 2 you should drop one if you find it or if you have an extra one. Bows don't trigger successive attacks.
Some weapons come with debuffs too. The majority of these debuffs are fine aside for continuous hp loss and attacks impaired on occasion -2, the latter will make half of your attacks do nothing. A caster should never pick this up but a melee player could get away with it if the weapon/passive itself is good.
GENERAL TIPS
If you're going to a night invader POI follow your team to the entrance and don't rush through it, you will aggro all the mobs. The entrance will allow you to pick off the invaders safely without trouble, do not use a recluse or ironeye ult here. Graces reset your downed status, so make sure you run by one if you're 2 or 3 barred before reaching the day end circle. Know boss weaknesses and resistances. Don't go using holy weapons against gargoyles/revenants or fire against wyrms. You cannot counteract continuous hp loss with the ED augur relic, it will just fuck you over if you don't have damage negation at full hp at all times.
Because this is a one-shot mode you need to be playing more cautiously. Trading is no longer an option. Don't go spamming attacks until your stamina runs out. If you're playing duchess I recommend you use a relic with dormant power discovers staves and stack magic damage. Please also try to learn the new map so you don't get lost and can help with breaking the crystals.