From The Heroes of Might and Magic III wiki

An Adventure map structure a hero can visit for some of Gold and Crystal.

The hero must defeat Dwarf guardians. More guardians means a better reward.

Probability %	Guardians	Reward
30	50 Battle Dwarves	2500 Gold and 2 Crystal
30	75 Battle Dwarves	4000 Gold and 3 Crystal
30	100 Battle Dwarves	5000 Gold and 5 Crystal
10	150 Battle Dwarves	7500 Gold and 10 Crystal

As with all Creature Banks, the troops are surrounded rather than facing the guardians across the normal battlefied, and no War Machines are used.

If only some of the guardians are killed they do not reset.