The guards of hell keep it hot and burning for the evil people.
Allah says in suratul alaq 96: 17-18
Then, let him call upon his council (of helpers), (17) We will call the guards of Hell (to deal with him)!
The leader of them is called maalik. Maalik has no mercy and kindness towards the kuffar. Allah says in suratul Zukhroof 43: 77-78
And they will cry: “O Malik (Keeper of Hell)! Let your Lord make an end of us.” He will say: “Verily you shall abide forever.” (77)
At Tahrim 66: 6
O you who believe! Ward off from yourselves and your families against a Fire (Hell) whose fuel is men and stones, over which are (appointed) angels stern (and) severe, who disobey not, (from executing) the Commands they receive from Allâh, but do that which they are commanded. (6)
Al Muddathir 74: 26-31
I will cast him into Hell-fire (26) And what will make you know (exactly) what Hell-fire is? (27) It spares not (any sinner), nor does it leave (anything unburnt)! (28) Burning and blackening the skins! (29) Over it are nineteen (angels as guardians and keepers of Hell). (30) And We have set none but angels as guardians of the Fire, and We have fixed number (19) only as a trial for the disbelievers, in order that the people of the Scripture (Jews and Christians) may arrive at a certainty [that this Qur’ân is the truth as it agrees with their Books regarding their number (19) which is written in the Taurât (Torah) and the Injeel (Gospel)] and that the believers may increase in Faith (as this Qur’ân is the truth) and that no doubt may be left for the people of the Scripture and the believers, and that those in whose hearts is a disease (of hypocrisy) and the disbelievers may say: “What Allâh intends by this (curious) example ?” Thus Allâh leads astray whom He wills and guides whom He wills. And none can know the hosts of your Lord but He. And this (Hell) is nothing else than a (warning) reminder to mankind. (31)
Al Ghafir 40: 49-50
And those in the Fire will say to the keepers (angels) of Hell: “Call upon your Lord to lighten for us the torment for a day!” (49) They will say: “Did there not come to you, your Messengers with (clear) evidences (and signs)? They will say: “Yes.” They will reply: “Then call (as you like)! And the invocation of the disbelievers is nothing but in vain (as it will not be answered by Allah)!” (50)
1. There are angels who will be guarding hell.
2. There are nineteen of these angels
3. The leaders are called Maalik
4. They will have no mercy or any kindness to the kuffar.