The 1d4 means that it is a random number, equally distributed, between 1 and 4. It is common terminology in D&D and other tabletop role-playing games.
The main strategy is to NOT start sweeping at the player's starting point. Even if you DO reveal something like a cultist on Floor 1, you can use the unswept squares as a wall to block its progress.
Rare items that I have found:
Sparkle Sword--1d12, but there are no strength bonuses.
Ancestor Sword--1d10, but summons an Ancestor if you miss with the sword.
Ring of Regeneration--Regen one HP every five turns or so.
Twin Crossbow--Double the damage of the regular crossbow, but uses up double the number of bolts!
About the number one thing missing from this game are speeds higher than Level 9. Actually reminds me of the one time I managed to clear Level 12 Height 5 on the NES version...
To kill a void eater, stay some distance until it starts to use its matter beam attack. Get to its side and then approach it before it fires to get a swing at it.
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