Chapter 4: Level 3 dungeon

"Any prep spells you wish to cast before engaging these creatures of the Mad Archmage?" she asks her companions.
After they have all answered, she will cast Spiritual Hammer before entering the cavern.
"When you are ready Nyx, give the command and we will engage."
Let me know if you like the positioning I made and you could do your first round turn already.
Please note that dwarfs are hanging 15 feet above the water chained to the ceiling.

Range: 60 feet
Target: See text
Components: V S
Duration: 1 minute
Classes: Cleric
You create a floating, spectral weapon within range that lasts for the duration or until you cast this spell again. When you cast the spell, you can make a melee spell attack against a creature within 5 feet of the weapon. On a hit, the target takes force damage equal to 1d8 + your spellcasting ability modifier. As a bonus action on your turn, you can move the weapon up to 20 feet and repeat the attack against a creature within 5 feet of it. The weapon can take whatever form you choose. Clerics of deities who are associated with a particular weapon (as St. Cuthbert is known for his mace and Thor for his hammer) make this spell’s effect resemble that weapon.
Armor Class: 18
Hit Points: 50
Speed: 30 ft., fly 40 ft.
STR DEX CON INT WIS CHA
16 (+3) 14 (+2) 16 (+3) 10 (+0) 14 (+2) 16 (+3)
Damage Resistances: radiant
Condition Immunities: charmed, frightened
Senses: darkvision 60 ft., passive Perception 12
Languages: Celestial, understands the languages you speak
Proficiency Bonus: 4
Actions: 2 attacks
Radiant Mace (Defender Only). Melee Weapon Attack: +8., Damage: 1d10+8 radiant, and the celestial can choose itself or another creature it can see within 10 feet of the target. The chosen creature gains 1d10 temporary hit points.
Healing Touch (1/Day). The celestial touches another creature. The target magically regains hit points equal to 2d8 + the spell’s level.
"Any prep spells you wish to cast before engaging these creatures of the Mad Archmage?" she asks her companions.
After they have all answered, she will cast Spiritual Hammer before entering the cavern.
"When you are ready Nyx, give the command and we will engage."
Unseen Nyx

Nyx scans the area one more time with his blindsight ad tremorsense. If nothing else catches his attention he releases his wildshape and readies his longbow.
Would my first attack have advantage as coming from being invisible or is it canceled and I do not get advantage?
Tante Lude summons a spiritual hammer to attack the dwarf to the party's north, following it with the death bell of a Toll the Dead cantrip. The Celestial flew at the one furthest to the east, striking two at him with his mace made of light.
Rolls
Spirit Hammer to hit - (1d20+8)
(2) + 8 = 10
Damage (force) - (1d8+4)
(8) + 4 = 12
Toll the Bell damage (necrotic) Wis save v. DC 15 - (2d8)
(73) = 10
If the Spiritual Weapon hit or the dwarf was hurt - (1d12)
(5) = 5
Celestial Mace - (1d20+8)
(19) + 8 = 27
Damage Radiant - (1d10+8)
(1) + 8 = 9
Celestial 2nd attack - (1d20+8)
(5) + 8 = 13
Damage Radiant - (1d10+8)
(9) + 8 = 17
Extra d12 (my mistake) on Toll the Dead v. damaged - (1d12)
(10) = 10
Rolls
Firebolt to hit - (1d20+8)
(16) + 8 = 24
Firebolt damage - (2d10)
(38) = 11
Range: 120 feet
Components: V, S
Duration: 1 round
A flash of light streaks toward a creature of your choice within range. Make a ranged spell attack against the target. On a hit, the target takes 4d6 radiant damage, and the next attack roll made against this target before the end of your next turn has advantage, thanks to the mystical dim light glittering on the target until then.
At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.
Rolls
Guiding Bolt - (Hit:1d20+8, radiant:4d6)
Hit:1d20+8 : (3) + 8 = 11
radiant:4d6 : (4135) = 13
Advantage - (1d20+8)
(10) + 8 = 18
Tante Lude could also observe that these particular undead are immune to necrotic damage

Rolls
Wisdom save against toll dead - (1d20+1)
(8) + 1 = 9