Sand Castle is an Orobas Ancient relic that makes the Act 2 Boss drop 2 relics. Unlike STS1, STS2 Bosses do not drop relics by default (relics come from each Act's Ancients). Sand Castle creates an exception and adds 2 relics to the Act 2 Boss reward. There is no rarity restriction on the drops, so lucky rolls can redirect the entire run.
Previously this relic used to upgrade 6 random cards, but an April 2026 patch swapped its effect with Lava Rock. Now it is the Boss-relic-drop effect.
The downside is there is no benefit between pickup and the Act 2 Boss. You have to endure the rest of Act 2 as an investment window. However, if you pick it up mid-Act 2 the distance to Boss is relatively short, so the waiting period is shorter than Lava Rock's old effect.
Character-Specific Ratings
| Character |
Rating |
Notes |
| Ironclad |
A |
High base HP makes Act 2 Boss clears safer, maximizing the 2-relic benefit |
| Silent |
B+ |
Act 2 stability is lower, but once Poison comes online Boss clears stabilize |
| Defect |
A |
With Orb setup nearly complete in late Act 2, Boss clears are stable |
| Necrobinder |
B+ |
If minions are ready, the Boss is fine; otherwise risky |
| Regent |
B+ |
Act 2 durability concerns exist, but 2 relics is a big return |
