Dragon's Herald
Creature — Goblin Shaman
, 
, Sacrifice a black creature, a red creature, and a green creature: Search your library for a card named Hellkite Overlord, put it onto the battlefield, then shuffle.
The penultimate step of the ritual involves bathing in a delicious glaze.
Daarken
Shards of Alara (ALA)
• #98Rulings
You may sacrifice multicolored creatures as part of the cost of the search ability. If you sacrifice a multicolored creature this way, specify which part of the cost that creature is satisfying.
(wotc • 2008-10-01)
You may sacrifice the Herald itself to help pay for the cost of its ability.
(wotc • 2008-10-01)
To activate the ability, you must sacrifice three different creatures. You can’t sacrifice just one three-colored creature, for example.
(wotc • 2008-10-01)
Rulings
You may sacrifice multicolored creatures as part of the cost of the search ability. If you sacrifice a multicolored creature this way, specify which part of the cost that creature is satisfying.
(wotc • 2008-10-01)
You may sacrifice the Herald itself to help pay for the cost of its ability.
(wotc • 2008-10-01)
To activate the ability, you must sacrifice three different creatures. You can’t sacrifice just one three-colored creature, for example.
(wotc • 2008-10-01)