Since you are new, I should offer you a couple of warnings about designed-in annoyances. The top tier Zombie monster, named Black Death, has a special case in the program that every time it strikes a character, your maximum hit points are permanently reduced by 1. There is no way (without cheats) to reverse this, ever. For this reason, most players refuse to play on levels with a Black Death and will immediately leave the level, if not the game, upon seeing one. According to Jarulf's Guide, section 5.2.1, page 84, Black Death may appear on dungeon levels 3-5 (second two of church, first of catacombs). They are not guaranteed to appear there, so you may roll some games where you can play those levels safely. According to Jarulf's Guide, section 5.3.2, pages 96-97, Black Death have a 13% chance to appear on dungeon level 3, 24% on dungeon level 4, and 23% on dungeon level 5.
Despite their name, they are a bright yellow and, like all Zombies, move slowly. If you react quickly upon seeing one, and exercise caution rounding corners, you are unlikely to be hit by one before you can see it and flee.
Also, there are three shrines you should never trigger. The Fascinating, Ornate, and Sacred shrines will each permanently reduce your maximum mana by 10%, in exchange for a token reward that you could easily get elsewhere for a trivial price. Like with Black Death, there is no way (without cheats) to reverse this, ever. Even worse, the Goat Shrine and the Cauldron act as a random shrine of the type that could appear on that level. You won't know which shrine type it is until you trigger it, at which point it's too late to decide that you don't want to use it. For this reason, you should be very careful not to use left-click attacks too close to Goat Shrines and Cauldrons, to avoid accidentally clicking on the shrine when you meant to click on something harmless, like treasure or an enemy. Right-click cannot trigger these shrines, so spellcasting characters may throw spells at enemies near these shrines without risk.[1] (Though you may want to avoid magically killing enemies near these shrines, since they might drop treasure next to the shrine, requiring you to exercise care to retrieve the treasure.) I don't remember if shift-click attacks can activate a shrine.
If you have not yet, I suggest you download a copy of Jarulf's Guide and keep it available while you play. It's more an encyclopedia of the game than a walkthrough. Using it, you can know the in-game message and effect of every named shrine. You can know in great detail how the game's combat mechanics work, the minimum and maximum statistics of monsters, the maximum statistics of each character class, how spells work, and more. The PDF is 167 pages in total, and none of it is wasted on screenshots.
[1] Except for Telekinesis, which can be used to trigger a shrine from a distance.
