Arthur can easily kill them using 'Demon's wrath' skill but he wanted to save mana to fight against lich. If lich can summon this many monsters in an instant, it can't be underestimated. The powerful 5 soldiers were also backing off after reaching a certain point.
Arthur flew by taking support from a undead soldier and used all his mana skills one after another and reached near the lich. Seeing Arthur lich said, "I am impressed. But it is of no use."
A shadow ball emerged in lich's right hand and he threw it on Arthur. Arthur dodged it and used his mana bomb and lich dodged it. This continued for some time.
Arthur understood that how large his mana would have be, it is still can't be comparable to the mana of lich and his undead monsters were also not able to hold the rest of monsters for a large time. So he decided to finish the lich as quickly as possible.
He has to engage in close combat with lich. So he started attacking lich using his powerful attacks like incinerate, fire blasts, mana beams and came closer to lich slowly. Arthur made a quick dash and used 'tiger palm force' on lich.
It was not a direct attack but lich's right hand was broken. Lich had recovered it instantly. Seeing that Arthur thought he had to use 'ultimate explosion' to explode lich. But he was not able to reach it.
Arthur once again used 'tiger palm force' attack but this time lich had blocked it with a barrier. Arthur understood that he had no other choice so he had to use 'explosion punch' skill. The skill Arthur thought never to use because of its high consumption of mana. If he use that attack now then it will be his last attack using mana.
Arthur wanted to take a chance he summoned a normal undead soldier on other side of lich and told him to attack. Lich had instantly killed the normal dead soldier using a 'shadow ball'. In that time Arthur made a dash towards lich charging his 'explosion punch' attack.
Lich sensed the Arthur and created a barrier. But Arthur's punch broke the barrier and his punch reached lich's body then-
'Booooooommm!!!'
There was a huge explosion and the dust covered entire floor. As the dust was slowly coming down, there were no dungeon monsters. Only Arthur's undead soldiers were there standing, facing towards Arthur. Arthur then cancelled his summon and all his undead soldiers disintegrated.
Then a round screen appeared on a wall. It started displaying words along with a speech. It said, "Congratulations Arthur Ischyros, you have cleared the dungeon successfully."
"For this achievement you got a 'mana core of this dungeon' as a reward."
"By absorbing this your all stats and skills will improve."
Saying this the screen disappeared and a mana orb was coming towards him.
Arthur touched the mana orb and it was getting absorbed by him. Arthur then saw his info. His all stats are improved along with the skills. He even got a new skill, "Ultimate Summoning". Using this skill he can summon a dead soul of a monster which was killed by his hands and can give it a new form. The revived soul will become Arthur's slave and follow his all orders.